FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

BRUCE HOPKINS,                          
                  Plaintiff-Appellee,
                 v.
A. BONVICINO, Badge No. 1140,
individually & in his official                No. 07-15102
capacity as a San Carlos Police
Officer; DAVID BUELOW                          D.C. No.
                                            CV-05-02932-JSW
individually & in his official
capacity as a San Carlos Police                OPINION
Officer; NICK NGUYEN, Badge No.
1141, individually in his official
capacity as a San Carlos Police
Officer; CITY OF SAN CARLOS,
             Defendants-Appellants.
                                        
        Appeal from the United States District Court
           for the Northern District of California
         Jeffrey S. White, District Judge, Presiding

                  Argued and Submitted
        October 20, 2008—San Francisco, California

                     Filed July 16, 2009

    Before: Mary M. Schroeder, Dorothy W. Nelson, and
             Stephen Reinhardt, Circuit Judges.

                 Opinion by Judge Reinhardt




                             9023
9028                HOPKINS v. BONVICINO




                        COUNSEL

Anthony Boskovich, Boskovich Law Office, San Jose, Cali-
fornia, for the plaintiff-appellee.

Todd H. Master, Howard Rome Martin & Ridley, Redwood
City, California, for the defendants-appellants.


                        OPINION

REINHARDT, Circuit Judge:

   On August 22, 2003, two San Carlos Police Officers broke
into Bruce Hopkins’ home. They did not have a warrant, nor
did they have probable cause. All that they had was a state-
ment from a third-party that Hopkins had been involved in an
                     HOPKINS v. BONVICINO                  9029
extremely minor traffic incident, an incident so minor that it
did not cause as much as a scratch on either of the vehicles
involved, and that he appeared to have been drinking. Based
on this information, the officers broke into Hopkins’ home
with their flashlights shining and their guns drawn. When they
found Hopkins, they handcuffed him, removed him from his
house, and placed him under arrest.

   The officers’ explanation for their warrantless entry is both
simple and audacious: They claim that, after hearing that
Hopkins had the smell of alcohol on his breath, they feared he
was on the brink of a diabetic coma and broke into his house
in order to offer medical assistance. According to one offi-
cer’s deposition testimony, they entered with their guns drawn
because individuals suffering from diabetic emergencies “may
sometimes be confused” and can be “combative.” Apparently,
in the officer’s view, someone suffering from such a medical
emergency may need to be deterred by deadly force. Hopkins,
however, was neither confused nor combative because he was
not suffering from a diabetic emergency — he was lying in
his bedroom watching television, which is where the officers
found him. Yet, after the officers discovered that he was per-
fectly healthy and non-comatose, they did not say “we’re glad
to see that you are safe, sir; we’ll be on our way now.” They
did not say, “Sorry for the disturbance and for damaging your
property.” No, instead they handcuffed Hopkins at gunpoint,
removed him from his home, placed him under arrest, and
brought him to the San Mateo County jail for the final chapter
in the case of the nonexistent diabetes.

   Hopkins sued the two officers who broke into his house,
their colleague who waited outside, and the City of San Car-
los under 42 U.S.C. § 1983. He asserts three causes of action:
unlawful warrantless entry of a home, unlawful arrest without
probable cause, and excessive use of force. The defendants
jointly moved for summary judgment on all counts — the
officers asserting a qualified immunity defense and the City
arguing that it should not be held liable under Monell v. N.Y.
9030                      HOPKINS v. BONVICINO
City Department of Social Services, 

(1978). The
district court denied the motion, and the defendant-officers
now appeal.1 Because “physical entry of the home is the chief
evil against which the wording of the Fourth Amendment is
directed,” Payton v. New York, 

, 585 (1980)
(quoting United States v. U.S. Dist. Court, 

, 313
(1972)), and because the officers’ conduct here unequivocally
violated Hopkins’ clearly established constitutional rights, we
affirm the denial of summary judgment with respect to Offi-
cers Bonvicino and Buelow, although we hold that their col-
league, Officer Nguyen, is entitled to qualified immunity.

           I.   Factual and Procedural Background

   On a Friday evening in late August of 2003, Bruce Hopkins
finished his shift at work and went to the local American
Legion Hall in San Carlos, California, for a drink.2 After hav-
ing a few beers he left to drive home. While en route, he was
involved in a minor traffic incident with a car driven by Ms.
Waheeda Talib. Both Talib and Hopkins agree that they each
got out of their cars to inspect the vehicles for damage.3
According to Hopkins, the two agreed that there was no dam-
age and he continued on his way home. According to later
police reports of the incident, Talib claimed that after exiting
his car Hopkins denied responsibility for the incident and sim-
ply drove away.

   Despite minor discrepancies in the details of the traffic
   1
     The denial of summary judgment with respect to the City of San Carlos
is not before us.
   2
     Because this case comes to us on defendants’ motion for summary
judgment, we take all facts in the light most favorable to Hopkins, the
nonmoving party.
   3
     Talib did not testify in any depositions for this lawsuit nor did she sub-
mit any affidavits or responses to interrogatories. Her statements are
drawn from the various police reports completed by the defendants in this
case.
                       HOPKINS v. BONVICINO                     9031
incident’s immediate aftermath, the parties agree that Talib
followed Hopkins to his home without Hopkins being aware
that she was behind him. When Hopkins arrived home and
left his car, Talib confronted him about the incident and
accused him of being intoxicated. Talib later told the
defendant-officers that she suspected Hopkins was under the
influence of alcohol because when she spoke with him in
front of his residence she smelled alcohol on his breath and
observed that he seemed impaired and had difficulty walking.
During her confrontation with Hopkins, Talib spoke on her
cell phone. Fearing that she was either calling “her husband
to come down there and beat [him] up or [that] she was call-
ing the cops,” Hopkins entered his house “as quick as he
could.” His exchange with Talib on his front lawn lasted no
longer than a minute to a minute and a half. Once inside his
home, Hopkins went to his bedroom in the basement to watch
television.

   Talib remained outside on Hopkins’ lawn and called the
police. She told the dispatcher that she had been involved in
a hit-and-run accident, that she followed the driver to his
house, and that she suspected he had been drinking. Shortly
thereafter, San Carlos police officers Armand Bonvicino and
Nick Nguyen arrived at Hopkins’ residence. Officer Bonvi-
cino, the “primary officer” for the call, asked Talib if she
needed medical assistance; she said she did not. Talib then
proceeded to tell Bonvicino and Nguyen about the traffic inci-
dent and reported that Hopkins appeared intoxicated when he
got out of his vehicle. Officer Bonvicino walked to the front
door of Hopkins’ house, knocked loudly, and announced him-
self as a police officer multiple times through an open win-
dow. He did not receive a response.

   Officer Bonvicino then returned to the front lawn and con-
ferred with Officer Nguyen and with Officer David Buelow,
who had since arrived at the scene.4 While Officer Nguyen
  4
    Officer Buelow had been Officer Bonvicino and Officer Nguyen’s
field training officer when they were both police department trainees.
9032                 HOPKINS v. BONVICINO
continued to interview Talib, Officers Bonvicino and Buelow
decided to walk to the side of the house in order to attempt
to contact Hopkins through a side door. The side entrance to
Hopkins’ home had a screen door, which was closed and
locked, and a solid door behind the screen, which was open.
After knocking on the screen door and receiving no response,
Officers Bonvicino and Buelow discussed with each other
possible explanations for Hopkins’ not answering. Among the
explanations they came up with was the possibility that Hop-
kins was on the brink of a diabetic coma. As both officers
later explained in their declarations and depositions, they had
been trained that what a layperson might describe as the odor
of alcohol on someone’s breath could actually be the “fruity”
smell associated with a diabetic emergency. With this poten-
tial medical emergency in mind, Officer Bonvicino loudly
announced through the screen that he and Officer Buelow
would be making an entry into the house to check on Hop-
kins’ welfare.

   Officer Bonvicino cut a hole in the screen, reached in, and
unlocked the door. He and Officer Buelow then entered the
residence with their flashlights on and their guns drawn.
Inside, the officers searched for Hopkins in the areas of his
home in which a person might be found. They discovered him
lying on the floor in his bedroom, which was a converted
garage space. According to Hopkins, he had never heard the
officers’ knocking and was terrified when they entered with
their guns drawn and flashlights shining; he fell off the bed
as they were coming down the stairs into his room. The offi-
cers asked Hopkins to get up, show his hands, and move
toward them, which he did. At this point, Officer Bonvicino
holstered his sidearm because, in his words, Hopkins “was not
a threat to officer safety.” Officer Buelow, however, contin-
ued to point his gun at Hopkins. Hopkins was then handcuffed
and taken outside.

  While Officers Bonvicino and Buelow were inside Hop-
kins’ home, Officer Nguyen had been interviewing Talib and
                        HOPKINS v. BONVICINO                 9033
taking pictures of her and Hopkins’ cars. Once Hopkins was
brought outside, Talib positively identified him as the driver
of the vehicle that had bumped into hers. After Officer
Nguyen explained the mechanics of a citizen’s arrest to her
and provided her with a citizen’s arrest form printed by the
San Carlos police department, Talib executed a citizen’s
arrest of Hopkins for hit-and-run and asked the officers to
take him into custody. The officers took Hopkins to the San
Carlos Police Department. He was later charged with hit-and-
run and driving under the influence and transferred to San
Mateo County Jail. Hopkins’ criminal charges were quickly
dropped once the judge in San Mateo Superior Court granted
his motion to suppress the evidence against him on the ground
that the officers’ entry into his home was illegal.

   After his criminal case concluded, Hopkins filed a civil
complaint under 42 U.S.C. § 1983 in the Northern District of
California, alleging, inter alia, that the officers violated his
civil rights by entering his house without a warrant, arresting
him without probable cause, and using excessive force. The
defendant-officers filed a joint motion for summary judgment,
contending that they did not violate Hopkins’ constitutional
rights, and, even if they did, that they are entitled to qualified
immunity. The district court granted the motion with respect
to Officer Nguyen’s liability for excessive force, but other-
wise denied the motion in all respects.

                  II.    Standard of Review

   A district court’s decision denying summary judgment on
the ground of qualified immunity is reviewed de novo. See,
e.g., Bingham v. City of Manhattan Beach, 

, 945
(9th Cir. 2003). Qualified immunity is “an entitlement not to
stand trial or face the other burdens of litigation.” Mitchell v.
Forsyth, 

, 526 (1985). Because the defense pro-
vides immunity from suit, not just a defense from liability, the
denial of a motion for summary judgment predicated on quali-
9034                  HOPKINS v. BONVICINO
fied immunity is an immediately appealable collateral order.

   The qualified immunity analysis involves two separate
steps. First, the court determines whether the facts “show the
officer’s conduct violated a constitutional right.” Saucier v.
Katz, 

, 201 (2001). If the alleged conduct did not
violate a constitutional right, then the defendants are entitled
to immunity and the claim must be dismissed. However, if the
alleged conduct did violate such a right, then the court must
determine “whether the right was clearly established” at the
time of the alleged unlawful action. 

is clearly
established if “a reasonable official would understand that
what he is doing violates that right.” 

If the right is
not clearly established, then the officer is entitled to qualified
immunity. While the order in which these questions are
addressed is left to the court’s “sound discretion,” “it is often
beneficial” to perform the analysis in the sequence outlined
above. Pearson v. Callahan, 

, 818 (2009). Of
course, where a claim of qualified immunity is to be denied,
both questions must be answered.

   When determining whether there are any genuine issues of
material fact at the summary judgment stage, the court must
take all facts in the light most favorable to the non-moving
party. In the context of qualified immunity, determinations
that turn on questions of law, such as whether the officers had
probable cause or reasonable suspicion to support their
actions, are appropriately decided by the court. Act
Up!/Portland v. Bagley, 

, 873 (9th Cir. 1993).
However, a trial court should not grant summary judgment
when there is a genuine dispute as to “the facts and circum-
stances within an officer’s knowledge” or “what the officer
and claimant did or failed to do.” 

Entry

  [1] Hopkins’ first claim is that his constitutional rights were
violated when, acting under color of state law, Officers Bon-
                     HOPKINS v. BONVICINO                   9035
vicino and Buelow entered his house without a warrant in vio-
lation of the Fourth Amendment. The Fourth Amendment
provides: “The right of the people to be secure in their per-
sons, houses, papers, and effects, against unreasonable
searches and seizures, shall not be violated . . . .” U.S. CONST.
amend. IV. “[S]earches and seizures inside a home without a
warrant are presumptively unreasonable.” United States v.
Martinez, 

, 1163 (9th Cir. 2005) (internal quo-
tation marks omitted) (quoting 

).

   [2] The presumption, however, is not irrebuttable. “There
are two general exceptions to the warrant requirement for
home searches: exigency and emergency.” 

These
exceptions are “narrow” and their boundaries are “rigorously
guarded” to prevent any expansion that would unduly inter-
fere with the sanctity of the home. United States v. Stafford,

, 1073 (9th Cir. 2005). In general, the differ-
ence between the two exceptions is this: The “emergency”
exception stems from the police officers’ “community car-
etaking function” and allows them “to respond to emergency
situations” that threaten life or limb; this exception does “not
[derive from] police officers’ function as criminal investiga-
tors.” United States v. Cervantes, 

, 889 (9th Cir.
2000) (emphasis added). By contrast, the “exigency” excep-
tion does derive from the police officers’ investigatory func-
tion; it allows them to enter a home without a warrant if they
have both probable cause to believe that a crime has been or
is being committed and a reasonable belief that their entry is
“necessary to prevent . . . the destruction of relevant evidence,
the escape of the suspect, or some other consequence improp-
erly frustrating legitimate law enforcement efforts.” United
States v. McConney, 

, 1199 (9th Cir. 1984) (en
banc).

   Here, the defendant-officers attempt to justify their war-
rantless entry into Hopkins’ home primarily on the basis of
the emergency exception, but rely in the alternative on the
exigency exception. We address these defenses in turn.
9036                      HOPKINS v. BONVICINO
                  A.    The Emergency Exception

   [3] This court has clearly held that a police officer may not
enter a home to investigate a medical emergency or other
immediate risk to life or limb unless he has “reasonable
grounds” to believe an emergency is at hand and that his
immediate attention is required. 

.
Although the test we announced in United States v. Cervan-
tes, 

(9th Cir. 2000), was altered by the Supreme
Court in Brigham City v. Stuart, 

(2006), the rea-
sonable grounds prong “survives Brigham City, and indeed
remains the core of the . . . analysis.” United States v. Snipe,

, 951 (9th Cir. 2008).5 Under this prong, “law
enforcement must have an objectively reasonable basis for
concluding that there is an immediate need to protect others
  5
   In Cervantes, we adopted a three part test for analyzing whether a war-
rantless entry is valid under the emergency exception. We held:
      (1) The police must have reasonable grounds to believe that there
      is an emergency at hand and an immediate need for their assis-
      tance for the protection of life or property. (2) The search must
      not be primarily motivated by intent to arrest and seize evidence.
      (3) There must be some reasonable basis, approximating probable
      cause, to associate the emergency with the area or place to be
      

. In Brigham, the Supreme Court intervened and altered
the analysis by abrogating the second prong of the Cervantes test. The
Court held that “[a]n action is ‘reasonable’ under the Fourth Amendment,
regardless of the individual officer’s state of mind, ‘as long as the circum-
stances, viewed objectively, justify [the] action.’ ” Brigham 

(emphasis and second alteration in original) (quoting Scott v.
United States, 

, 138 (1978)).
   We then construed Brigham as requiring that officers executing a war-
rantless entry of a home “ha[ve] an objectively reasonable basis for con-
cluding that there [i]s an immediate need to protect others or themselves
from serious harm; and [that] the search’s scope and manner [a]re reason-
able to meet the need.” 

. This formulation, when
combined with the third prong of Cervantes, which was unaffected by
either Brigham or Snipe, states our circuit’s current law governing the
emergency exception.
                     HOPKINS v. BONVICINO                  9037
or themselves from serious harm.” 

(emphasis
added). This “reasonable basis” requirement, clearly estab-
lished by Cervantes in 2000 and reaffirmed by Snipe in 2008,
is the core principle governing the officers’ conduct in the
present appeal.

   We must “judge whether or not the emergency exception
applies in any given situation based on the totality of the cir-
cumstances, and, as with other exceptions to the warrant
requirement, the Government bears the burden of demonstrat-
ing that the search at issue meets these parameters.” United
States v. Stafford, 

, 1074 (9th Cir. 2005). Here,
the defendant-officers contend that two possible medical
emergencies justified their warrantless entry.

   [4] The officers’ first argument is that because they were
responding to a reported automobile accident they were
authorized to enter Hopkins’ home to see if he was injured as
a result of that incident. However, taking the alleged facts in
the light most favorable to Hopkins, the police officers were
aware that the purported accident did not cause so much as a
scratch to either of the cars involved, as is confirmed by the
photographs of the vehicles taken that evening by Officer
Nguyen. Furthermore, after speaking with Talib — the
woman who called the police and spoke with them before
they entered Hopkins’ home, who was involved in the so-
called “accident,” and who observed Hopkins exit his car both
at the scene of the incident and back at his home — the offi-
cers, in their own words, learned “nothing” regarding the
nature of the accident that “caused [them] to be concerned for
Mr. Hopkins’ medical condition.” In short, there was abso-
lutely no indication that the minor bump between the two cars
was at all serious or that it had caused any type of medical
emergency. Accordingly, the mere fact that the officers were
responding to a minor “hit-and-run” cannot justify their war-
rantless entry into Hopkins’ home.
9038                      HOPKINS v. BONVICINO
   [5] Perhaps aware of the tenuous nature of this first argu-
ment, the officers put greater weight on their second pur-
ported medical emergency: the argument that they had reason
to believe that Hopkins was suffering from or on the brink of
a diabetic coma. This claim, however, is equally baseless,
and, if permitted to serve as the basis for the warrantless home
intrusion, would allow police officers to ignore the Fourth
Amendment almost at will. No one disputes that a diabetic
coma is a medical emergency, which it clearly is. Rather, the
question before us is whether Officers Bonvicino and Buelow
had an “objectively reasonable basis” to suspect that Hopkins
was in fact suffering from a diabetic coma. 

. Taking the facts in the light most favorable to Hopkins,
the only information the officers possessed that would support
such a conclusion is as follows: (1) Talib said she smelled
alcohol on Hopkins’ breath; (2) Talib described Hopkins as
appearing slightly intoxicated; and (3) Hopkins did not
respond when the officers knocked on his door. The officers
argue that, because an individual suffering from the initial
phases of a diabetic coma can, to an untrained observer,
appear intoxicated and can have a “sickly sweet” or “fruity”
odor on his breath that a layperson might confuse with the
smell of alcohol, their fear of a diabetic emergency was rea-
sonable. This contention is unsupportable: the mere sugges-
tion that someone has a smell resembling alcohol on his
breath and appears slightly intoxicated does not create “rea-
sonable grounds” to suspect a diabetic emergency sufficient
to justify warrantless entry into a home. If it did, then, as the
officers acknowledged at oral argument, any time the police
receive information from a layperson that someone inside a
home has the appearance of a person who has consumed alco-
hol the police will be authorized to enter that home without
a warrant. This result would expand the “narrow[,] . . . rigor-
ously guarded exception[ ] to th[e] warrant requirement”
beyond all recognition, and simply cannot be the law. Staf-

.6
  6
   The officers’ contention is especially troubling in light of the large per-
centage of police activity that involves some report of alcohol consump-
                         HOPKINS v. BONVICINO                         9039
   [6] As this court has made clear, “if [police officers] other-
wise lack reasonable grounds to believe there is an emergen-
cy,” they must “take additional steps to determine whether
there [i]s an emergency that justifie[s] entry in the first place.”
United States v. Russell, 

, 1092 (9th Cir. 2006).
Here, the officers did not take any such additional steps. They
did not, as in Martin v. City of Oceanside, 

,
1080 (9th Cir. 2004), attempt to reach Hopkins by telephone
in order to check on his welfare. They did not ask Talib for
more information, such as whether she observed Hopkins
wearing a medical alert bracelet or whether the odor she
smelled on his breath was “fruity,” “sickly sweet,” or other-
wise distinguishable from the typical smell of alcohol on a
person’s breath. The mere fact that Hopkins did not answer
the door cannot tip the balance in the officers’ favor, since
nothing requires an individual to answer the door in response
to a police officer’s knocking. United States v. Washington,

, 1070-71 (9th Cir. 2004). We do not dispute
that the police officers in this case had reasonable grounds to
believe that Hopkins had been drinking, but, without obtain-
ing more information, they could not reasonably have
believed that he needed immediate medical attention due to a
diabetic emergency.7

  [7] Every case in this circuit that has upheld a warrantless
search of a home under the emergency exception has involved

tion. See generally BUREAU OF JUSTICE STATISTICS, ALCOHOL AND CRIME
(1998) (reporting high correlation between alcohol involvement and sus-
pected or actual criminal conduct), available at http://www.ojp.usdoj.gov/
bjs/pub/pdf/ac.pdf.
   7
     We also note that under United States v. Snipe, 

note 5, we
“must consider the officers’ manner of 

. Here, the
officers entered the house with their guns drawn, a tactic that hardly seems
consistent with a response to a medical emergency where the victim is
expected to be comatose or quasi-comatose. Surely paramedics or emer-
gency medical technicians responding to diabetic emergencies do not do
so with guns drawn.
9040                 HOPKINS v. BONVICINO
significantly more evidence of an emergency than is present
here. In Cervantes itself, the searching officer, who had been
trained to recognize the smell of highly combustible fumes
associated with methamphetamine production, personally
smelled those fumes emanating from an apartment after
responding to a call from the fire 

. In United States v. Bradley, a mother who had just
been arrested for possessing methamphetamine told the police
that her nine-year old son was home alone in the middle of the
night, a situation that we held “requir[ed] immediate police
assistance.” 

, 1215 (9th Cir. 2003). In Martin
v. City of Oceanside, officers entered a house in response to
a phone call from a father who called the police “with an
urgent request to check on the safety of his daughter . . .
[whom he] had been unable to reach . . . for several 

. In United States v. Martinez, officers
responding to a domestic violence call found a woman crying
on the front lawn of a house and heard a man shouting from
inside; in the unique context of “a domestic abuse call, [in
which] ‘violence may be lurking and explode with little warn-
ing,’ ” we upheld the officers’ warrantless entry to speak to
the screaming and potentially injured male 

(quoting Fletcher v. Clinton, 

, 50 (1st
Cir. 1999)). In United States v. Stafford, we upheld a warrant-
less entry after a building maintenance man reported to police
that the walls of an apartment were covered in blood and
feces and that he smelled what he thought was a dead body.

, 1071-73 (9th Cir. 2005). In United States v.
Russell, we upheld a warrantless entry where a series of con-
fused 911 calls suggested that one individual had shot another
inside a house and that the shooter was still inside when the
officers arrived. 

, 1090 (9th Cir. 2006). Finally,
in United States v. Snipe, the police entered a home in
response to a 911 call in which a “very hysterical sounding”
caller “screamed . . . [g]et the cops here 

(alteration in original).

   [8] A statement that someone’s breath smelled like alcohol
is not even remotely comparable to the information we have
                     HOPKINS v. BONVICINO                  9041
previously deemed to constitute “reasonable grounds” for sus-
pecting a medical or other life-threatening emergency. It is
simply inconceivable that a “reasonable officer” presented
with the information that Talib conveyed to Officers Bonvi-
cino and Buelow could conclude, on the basis of that informa-
tion alone, that he had “an objectively reasonable basis” to
suspect a medical emergency was at hand. Yet, as Officer
Buelow acknowledged in his deposition, he believed that,
hypothetically, any time an officer receives a report of alcohol
consumption, that officer would, in his discretion, have rea-
sonable grounds to enter a home without a warrant in order
to investigate a diabetic emergency. Whatever this under-
standing of the Fourth Amendment might be called, it cannot
be called “objectively reasonable.” Thus, the emergency
exception cannot justify the warrantless entry into Hopkins’
home.

                B.   The Exigency Exception

   [9] The officers’ alternative argument is that, although they
claim to have entered Hopkins’ house in response to a medi-
cal emergency, a reasonable officer would have been justified
in entering the building in order to investigate a crime under
the “exigent circumstances” exception. “[W]hen the govern-
ment relies on the exigent circumstances exception, it . . .
must satisfy two requirements: first, the government must
prove that the officer had probable cause to search the house;
and second, the government must prove that exigent circum-
stances justified the warrantless intrusion.” United States v.
Johnson, 

, 905 (9th Cir. 2001) (en banc). “Exi-
gent circumstances” can include “the destruction of relevant
evidence.” United States v. McConney, 

, 1199
(9th Cir. 1984) (en banc). Here, the officers claim that their
entry was justified because a reasonable officer would have
had probable cause to believe Hopkins had been driving under
the influence of alcohol in violation of CAL. VEH. CODE
§ 23152, and that an immediate entry was necessary in order
9042                      HOPKINS v. BONVICINO
to obtain evidence of his blood alcohol content before the
alcohol in his bloodstream metabolized.

  We address the probable cause and exigent circumstances
requirements in turn.

                         1.    Probable Cause

   [10] As the officers concede, the only crime for which they
can claim to have had probable cause to enter Hopkins’ resi-
dence is driving under the influence of alcohol, a violation of
CAL. VEH. CODE § 23152.8 “Officers have probable cause for
a search when ‘the known facts and circumstances are suffi-
cient to warrant a man of reasonable prudence in the belief
that contraband or evidence of a crime will be found.’ ”
United States v. Henderson, 

, 648 (9th Cir. 2000)
(quoting Ornelas v. United States, 

, 696 (1996)).

   [11] This court has held that “[i]n establishing probable
cause, officers may not solely rely on the claim of a citizen
witness that [s]he was a victim of a crime, but must indepen-
dently investigate the basis of the witness’ knowledge or
interview other witnesses.” Arpin v. Santa Clara Valley
Transp. Agency, 

, 925 (9th Cir. 2001) (citing
Fuller v. M.G. Jewelry, 

, 1444 (9th Cir. 1991)
(“[P]olice officers ha[ve] a duty to conduct an investigation
into the basis of [a] witness’ report”)). In violation of the rule
set forth in Arpin and Fuller, the officers here entered Hop-
kins’ home based solely on the information they obtained
  8
    The officers expressly waived below any argument that investigation
of a potential hit-and-run could have justified their warrantless entry. They
also acknowledge in their briefs on appeal that Talib’s citizen’s arrest, dis-
cussed infra Part IV.B, “is not a basis for [their] warrantless entry into the
residence.” And so they must, as their own police reports indicate that
Talib did not authorize a citizen’s arrest until after the officers entered
Hopkins’ home. Even if a stand-alone citizen’s arrest could justify a war-
rantless home entry — a dubious proposition, see infra Part IV.B — the
sequence of events here does not support such a justification.
                        HOPKINS v. BONVICINO                        9043
from Talib — namely, that she had been involved in an
extremely minor car accident with Hopkins, that she smelled
alcohol on his breath, and that he appeared intoxicated. The
officers did not inspect Hopkins’ car to see if the hood was
still warm, cf. People v. Thompson, 

, 5-8 (Cal.
2006), which would have corroborated Talib’s statement that
the car had recently been driven, nor did they inspect the vehi-
cle for any evidence of reckless driving or of alcohol con-
sumption, such as open containers or an alcoholic odor. They
did not ask Talib any questions in order to gain information
beyond her cursory and conclusory statements, such as
whether she observed Hopkins driving erratically or at an
abnormal speed. In short, the officers obtained no information
whatsoever beyond Talib’s brief statement. Under Arpin and
Fuller, these statements from a witness, without further inves-
tigation by the police, are insufficient to support probable cause.9

                   2.    Exigent Circumstances

   Even if the officers had probable cause that Hopkins had
been driving under the influence (and even if that would have
been sufficient for entry into his home pursuant to a warrant),
more is required to justify a warrantless entry into his house.
The Fourth Amendment requires that there be exigent circum-
stances for a warrantless entry. See, e.g., 

. The defendants contend that a reasonable officer
would have been justified in entering Hopkins home in order
   9
     We need not decide whether even if the officers had obtained indepen-
dent evidence supporting Talib’s allegations, the “probable cause” this
information provided would have been sufficient to justify the issuance of
a warrant to search Hopkins’ home for evidence of the minor misdemea-
nor violation at issue here. Whether a home, or the homeowner in his
home, may be searched pursuant to a warrant for evidence of a minor
motor vehicle violation involving neither personal injury nor property
damage raises a serious question in our minds and would require the bal-
ancing of the interests of the homeowner in the right to privacy in his
home versus the state’s interest in searching homes for evidence of such
minor criminal violations.
9044                 HOPKINS v. BONVICINO
to obtain evidence of his blood-alcohol ratio, and that the
rapid metabolizing of the alcohol in his blood would consti-
tute exigent circumstances. This argument would seem to be
directly foreclosed by Welsh v. Wisconsin, a case in which the
United States Supreme Court held that “a warrantless home
arrest cannot be upheld simply because evidence of the peti-
tioner’s blood-alcohol level might have dissipated while the
police obtained a warrant.” 

, 754 (1984); see also

(holding that the same analysis applies to “agents
of the government who seek to enter the home for purposes
of search or arrest”). Welsh involved an investigation of
alleged misdemeanor drunk driving, just as did Hopkins’ case.
However, relying on People v. Thompson, 

(Cal.
2006), a California Supreme Court decision, the officers argue
that Welsh is distinguishable because the Wisconsin DUI law
at issue in that case was a “nonjailable” offense, whereas in
California DUI is a misdemeanor punishable by up to six
months in county jail.

   [12] The appellants are correct that three years after they
broke into Hopkins’ home the California Supreme Court
sought to distinguish Welsh on the basis of a difference
between jailable and nonjailable offenses. See 

(“We
therefore believe Welsh was limited to Wisconsin’s ‘amazing’
decision to classify DUI as a civil nonjailable offense
. . . .”). However, this is not the distinction that the United
States Supreme Court drew in Welsh, nor is it the distinction
that this circuit has repeatedly emphasized in its own
exigency-exception decisions. To the contrary, in Welsh the
Supreme Court held that the exigency analysis must turn on
“the gravity of the underlying 

(emphasis added), not its status as “jailable” or “nonjailable.”
The Court specifically said that a finding of exigent circum-
stances is particularly inappropriate “when the underlying
offense . . . is realtively minor,” 

(emphasis added),
and cited favorably “those courts addressing the issue [that]
have refused to permit warrantless home arrests for nonfelo-
nious crimes.” 

(emphasis added). The Supreme
                        HOPKINS v. BONVICINO                      9045
Court expressly did not limit its holding in Welsh to nonjail-
able offenses,10 see 

to the contrary, it suggested that
exigent circumstances can rarely, if ever, support entry into a
home to investigate or arrest someone for a misdemeanor
offense.

   [13] Building on the felony/misdemeanor distinction dis-
cussed in Welsh, this circuit has clearly held that “an exigency
related to a misdemeanor will seldom, if ever, justify a war-
rantless entry into the home.” LaLonde v. County of Riverside,

, 956 (9th Cir. 2000) (citing 

). In United States v. Johnson, we analyzed en banc a
warrantless search of a home and noted that “in situations
where the underlying offense is only a misdemeanor, law
enforcement must yield to the Fourth Amendment in all but
the ‘rarest’ cases.” 

, 909 n.6 (9th Cir. 2001) (en
banc) (quoting 

). Because Johnson and
LaLonde relied on and directly cited Welsh for the proposition
that investigation of a misdemeanor will rarely, if ever, sup-
port exigent circumstances, see 

08, it is clear that,
whatever “rare” circumstances might justify a warrantless
home entry to investigate a misdemeanor, misdemeanor driv-
ing while under the influence, the very offense at issue in
Welsh and cited by Johnson, does not fall within that very
narrow exception. Here, the offense that the officers claim
supports their warrantless entry is indisputably a misdemea-
nor, see CAL. VEH. CODE §§ 23152, 23536; CAL. PENAL CODE
§ 17 (2008) (defining misdemeanor). More important, it is the
precise offense that the Supreme Court held insufficient to
justify a warrantless entry in Welsh. Accordingly, even were
there probable cause that Hopkins had in fact been driving
under the influence, a warrantless entry into his home was
unjustified.
  10
    In fact, the offense for which Welsh himself was ultimately charged
was a jailable offense under Wisconsin law, although the offending offi-
cers did not know this at the time they entered his home. See 

n.6.
9046                  HOPKINS v. BONVICINO
   The fact that the California Supreme Court expressed its
disagreement with the United States Supreme Court several
years after the officers broke into Hopkins’ home and that it
took a different view of the Fourth Amendment than this cir-
cuit and the United States Supreme Court does not alter our
conclusion in this case. It is the federal courts that are the
final arbiters of federal constitutional rights, not the state
courts. See, e.g., Bennett v. Mueller, 

, 582 (9th
Cir. 2003) (“[S]tate courts will not be the final arbiters of
important issues under the federal constitution.” (quoting
Minnesota v. Nat’l Tea Co., 

, 557 (1940))). This
court’s precedents make clear that a warrantless home entry
to obtain evidence of a misdemeanor offense is “seldom, if
ever” constitutional, and that it was certainly unconstitutional
here. 

.

   Accordingly, the exigency exception is inapplicable here
for two independent reasons — absence of probable cause and
absence of exigent circumstances — either of which is suffi-
cient to compel our holding that the officers’ forced entry into
Hopkins’ home violated his Fourth Amendment rights.

                     C.   Officer Nguyen

   [14] To this point, we have discussed the conduct of Offi-
cer Buelow and Officer Bonvicino, but not the conduct of
Officer Nguyen, who remained outside with Talib while his
colleagues broke into Hopkins home. The district court
granted Officer Nguyen’s motion for summary judgment with
respect to Hopkins’ claim of excessive force, but denied the
motion with respect to the unlawful entry claim. Hopkins
argues that Officer Nguyen should not enjoy qualified immu-
nity on the warrantless-entry claim because Nguyen was an
“integral participant” in the search. This argument, however,
misunderstands our circuit precedent. In Chuman v. Wright,

(9th Cir. 1996), we rejected “the ‘team effort’
standard [that] allows the jury to lump all the defendants
together, rather than require it to base each individual’s liabil-
                        HOPKINS v. BONVICINO                       9047
ity on his own 

. In that case, we held
that a police officer’s “[b]eing a mere bystander [to his col-
leagues’ conduct] was insufficient” to support § 1983 liabil-
ity. 

   [15] Hopkins seeks to distinguish Chuman by relying on
the “integral participant” rule, which, as its name suggests,
extends liability to those actors who were integral participants
in the constitutional violation, even if they did not directly
engage in the unconstitutional conduct themselves. However,
this rule requires more participation and support on the part
of a particular defendant than the undisputed facts in this case
show Officer Nguyen to have provided. Under the integral
participant rule, “an officer who does not enter an apartment,
but stands at the door, armed with his gun, while other offi-
cers conduct the search, can . . . be a ‘full, active participant’
in the search” and therefore can be subject to § 1983 liability.
Boyd v. Benton County, 

, 780 (9th Cir. 2004)
(emphasis added). Each of the cases cited in Boyd in which
the “integral participant” rule was deemed satisfied involved
officers who “provided armed backup during an unconstitu-
tional search.” 

“integral participant” rule may
extend liability beyond simply those officers who provide
“armed backup,” it is clear that an officer who waits in the
front yard interviewing a witness and does not participate in
the unconstitutional search in any fashion cannot be held lia-
ble under Chuman.

   [16] Hopkins argues that Officer Nguyen is not entitled to
qualified immunity because he was part of a conversation in
which the three officers formed a “plan of action” to enter the
house. However, the undisputed facts show that the decision
to enter Hopkins’ home was not made or discussed during that
conversation, but rather was made in a separate conversation
between Officers Buelow and Bonvicino at the side entrance
to Hopkins’ house.11 Accordingly, Officer Nguyen partici-
  11
    We also note that there is no allegation that Officer Nguyen either
ordered the unconstitutional search or directed it from afar. To the con-
9048                     HOPKINS v. BONVICINO
pated in neither the planning nor the execution of the unlawful
search. We therefore reverse the district court with respect to
Officer Nguyen’s liability and hold that he is entitled to quali-
fied immunity on the unlawful search claim.

                  D.    Clearly Established Law

   Because Officer Nguyen did not commit a constitutional
violation with respect to Hopkins’ warrantless-entry claim, we
need not proceed to the second step of the qualified-immunity
analysis with respect to him. However, because both Officer
Bonvicino and Officer Buelow did violate Hopkins’ Fourth
Amendment rights by forcibly entering his home without a
warrant in the absence of any valid justification under either
the emergency or exigency exceptions, in order to determine
whether they are entitled to qualified immunity on this claim
we must examine whether the contours of those two excep-
tions were clearly established in 2003 when they engaged in
the conduct at issue.

   [17] To begin with the emergency exception, our decision
in United States v. Cervantes clearly establishes that at the
time of the officers’ warrantless forced entry into Hopkins’
home “[t]he police [were required to] have reasonable
grounds to believe that there is an emergency at hand and an
immediate need for their 

. That
opinion, which set forth the governing legal standard, was

trary, the record is clear that Officer Bonvicino was the “primary agent”
on the scene. It is also clear that Officer Buelow was the most senior offi-
cer, as he had been both Officer Bonvicino’s and Officer Nguyen’s Field
Training Officer. Thus, the rule that “[a] supervisor may be held liable
under § 1983 ‘if he or she was personally involved in the constitutional
deprivation or a sufficient causal connection exists between the supervi-
sor’s unlawful conduct and the constitutional violation’ ” does not apply
to Officer Nguyen. Lolli v. County of Orange, 

, 418 (9th Cir.
2003) (quoting Jackson v. City of Bremerton, 

, 653 (9th Cir.
2001)).
                     HOPKINS v. BONVICINO                 9049
decided in June of 2000, over three years before Officers Bue-
low and Bonvicino engaged in their warrantless entry. Our
previous discussion, 

Part III.A, makes clear that it
was patently unreasonable for Buelow and Bonvicino to
believe that a diabetic emergency was at hand based simply
on Talib’s description of Hopkins as slightly inebriated. Our
qualified immunity analysis, however, presents a somewhat
different question than whether there were “reasonable
grounds to believe that there [wa]s an emergency at hand;” id;
in determining whether the officers’ conduct violated clearly
established law, we must ask whether in 2003 a “reasonable
officer” would have known that he lacked “reasonable
grounds to believe that there [wa]s an emergency at hand.”
See Saucier v. Katz, 

, 202 (2001); Robinson v.
Solano County, 

, 1012 (9th Cir. 2002) (en banc)
(“[T]he standard of reasonableness for purposes of qualified
immunity is distinct from the standard of reasonableness
embodied in the Fourth Amendment.”). Here, we unhesitat-
ingly conclude that a reasonable officer would indeed have
known that the emergency exception to the Fourth Amend-
ment would not encompass a warrantless entry into a home
based solely on statements from a third party that an individ-
ual inside the home appeared inebriated prior to entering the
residence. No reasonable officer, indeed no reasonable per-
son, upon hearing that someone appeared or smelled some-
what inebriated could, without any further information,
reasonably conclude that such a person was on the brink of a
diabetic coma. To the contrary, a reasonable officer hearing
such a description would conclude that the individual had
consumed alcohol — conduct that would most certainly not
justify a warrantless entry into a home. As we have previously
held, when there is a “complete lack of evidence that would
support a reasonable suspicion,” and the officers have pro-
vided a “wholly inadequate justification for the[ir] search, we
conclude that it would have been clear to a reasonable officer
that [such a search] was unlawful.” See Ramirez v. City of
Buena Park, 

, 1023 (9th Cir. 2009). Similarly,
9050                 HOPKINS v. BONVICINO
in 2003, no reasonable officer would have believed that,
where a two-car automobile incident resulted in damage to
neither car and the drivers of both cars drove off without any
apparent physical complaint or difficulty, he should be suffi-
ciently concerned about possible injuries to one of the drivers
to forcibly enter his home in order to conduct an investigation
regarding his possible injuries. As a result, the defendants are
not entitled to qualified immunity under the emergency
exception.

   [18] As for the exigency exception, both our conclusions
that the officers lacked probable cause to enter Hopkins’
home and that an investigation of a potential misdemeanor
drunk-driving incident does not create an exigent circum-
stance were clearly established at the time the officers broke
into the plaintiff’s home. As to probable cause, this court
determined as early as 1991 that “police officers ha[ve] a duty
to conduct an investigation into the basis of [a] witness’
report” and that absent such investigation the report alone
does not support probable cause. Fuller v. M.G. Jewelry, 

, 1444 (9th Cir. 1991). This rule was reaffirmed a
mere two years before the conduct at issue in this case. See
Arpin v. Santa Clara Valley Transp. Agency, 

,
925 (9th Cir. 2001). It was equally clearly established by 2003
that “an exigency related to a misdemeanor will seldom, if
ever, justify a warrantless entry into the home.” LaLonde v.
County of Riverside, 

, 956 (9th Cir. 2000). More-
over, we made clear a year later, in United States v. Johnson,
that “where the underlying offense is only a misdemeanor,”
such as the misdemeanor drunk-driving at issue in Welsh,
“law enforcement must yield to the Fourth Amendment.” 

, 909 n.6 (9th Cir. 2001) (en banc) (quoting 

).

   [19] The California Supreme Court’s decision in People v.
Thompson distinguishing Welsh cannot alter our conclusion
that the prohibition of warrantless entry into a home to inves-
tigate misdemeanor drunk-driving was “clearly established” at
                     HOPKINS v. BONVICINO                   9051
the time Officers Buelow and Bonvicino broke into Hopkins’
home. For one thing, Welsh, LaLonde, and Johnson — bind-
ing precedents from the Supreme Court and this court clearly
establishing that rule — all predate the conduct underlying
this lawsuit, whereas People v. Thompson was decided three
years after the officers’ unconstitutional action. Furthermore,
a decision by a state court contrary to a holding of this court
cannot unsettle or “de-establish” the clarity of federal law.
Although “[t]he Supreme Court has provided little guidance
as to where courts should look to determine whether a particu-
lar right was clearly established at the time of the injury,” we
have held that “[i]n the Ninth Circuit, we begin our inquiry by
looking to binding precedent. If the right is clearly established
by decisional authority of the Supreme Court or this Circuit,
our inquiry should come to an end.” Boyd v. Benton County,

, 781 (9th Cir. 2004) (internal citation omitted)
(citing Capoeman v. Reed, 

, 1514 (9th Cir.
1985)). Thus, with respect to the lack of probable cause and
the lack of exigent circumstances — the absence of either one
of which would preclude the officers’ reliance on the exi-
gency exception — the law as to both was clearly established
in 2003 and the officers are not entitled to qualified immunity
on the basis of that exception. Because it was also clearly
established that the officers’ conduct did not fall within the
emergency exception, the two defendants are not entitled to
qualified immunity on that basis either. Accordingly, the offi-
cers were properly denied summary judgment as to Hopkins’
warrantless-entry claim.

           IV.   Arrest Without Probable Cause

   The officers also appeal the denial of their qualified-
immunity defense with respect to Hopkins’ claim of unlawful
arrest. This claim encompasses two different arrests: one that
occurred inside Hopkins’ home, and a second that occurred
9052                     HOPKINS v. BONVICINO
once he was brought outside and placed under citizen’s arrest.
We analyze the two arrests separately.12

                 A.    Arrest In Hopkins’ Home

   The Fourth Amendment protects against warrantless arrest
inside a person’s home in the same fashion that it protects
against warrantless searches of the home, which is to say that
police officers may not execute a warantless arrest in a home
unless they have both probable cause and exigent circum-
stances. See, e.g., 

(“It is a ‘basic prin-
ciple of Fourth Amendment law’ that searches and seizures
inside a home without a warrant are presumptively unreason-
  12
     In Fisher v. City of San Jose, 

(9th Cir. 2008) (en banc),
this court held that an “armed standoff was a single Fourth Amendment
event, a continuous process of formalizing [an] arrest.” 

Here,
by contrast, two distinct seizures took place, one occurring after the other
was already accomplished. Drawing a distinction between two consecutive
and overlapping “seizures” is a common and longstanding practice in
Fourth Amendment jurisprudence, as in the case of so-called “Terry
stops,” see Terry v. Ohio, 

, 16-19 (1968); see also, e.g., Rohde
v. City of Roseburg, 

, 1144 (9th Cir. 1998), or of unconstitu-
tionally excessive force, see Chavez v. Martinez, 

, 773 n.5
(2003) (plurality opinion); Graham v. Connor, 

, 388, 394
(1989); Pierce v. Multnomah County, 

, 1042 (9th Cir. 1996)
(quoting Robins v. Harum, 

, 1010 (9th Cir. 1985)). These
longstanding precedents demonstrate that generally an individual who has
already been seized can still be further seized for purposes of the Fourth
Amendment — a proposition that is not inconsistent with Fisher’s holding
that Fourth Amendment infringements suffered between the initiation of
a seizure and the perfection, or “formalizing,” of that same seizure may
not be analyzed independently for purposes of the warrant requirement.

.
   Here, Hopkins’ second seizure did not occur in the “process of formal-
izing” his first seizure, 

accomplished, at the latest, when
he was led from his house in handcuffs. See infra 34-35. Rather, much like
a Terry stop followed by a formal arrest, the first seizure here preceded
the second. Accordingly, the two arrests were independent Fourth Amend-
ment events that can independently support separate causes of action
under § 1983.
                     HOPKINS v. BONVICINO                  9053
able.”); 

(“[W]arrantless . . . arrests in
the home are prohibited by the Fourth Amendment, absent
probable cause and exigent circumstances.”). In light of the
above, because Hopkins was in fact seized inside his home,
Officers Buelow and Bonvicino violated his Fourth Amend-
ment rights by arresting him without a warrant for the same
reasons that their emergency and exigency defenses fail to
justify their warrantless entry. 

Part III.B.

   An arrest — or, to use the Fourth Amendment’s terminol-
ogy, a “seizure” — “occurs when a law enforcement officer,
through coercion, ‘physical force[,] or a show of authority, in
some way restricts the liberty of a person.’ ” United States v.
Washington, 

, 1069 (9th Cir. 2004) (quoting
United States v. Chan-Jimenez, 

, 1325 (9th Cir.
1997)). “A person’s liberty is restrained when, ‘taking into
account all of the circumstances surrounding the encounter,
the police conduct would have communicated to a reasonable
person that he was not at liberty to ignore the police presence
and go about his business.’ ” 

v. Bostick,

, 437 (1991)). Here, taking the facts in the light
most favorable to Hopkins, Officers Buelow and Bonvicino
entered his home with guns drawn, ordered him to show his
hands, told him that he was under arrest, handcuffed him, and
took him outside. Under these circumstances, it is clear that
the officers restricted his liberty and seized him. See, e.g.,
United States v. Washington, 

, 772 (9th Cir.
2007) (considering fact of police officer’s “directing [some-
one] where to walk” in holding that a seizure occurred);
United States v. Manzo-Jurado, 

, 934 n.3 (9th
Cir. 2006) (holding that a police officer’s order to occupants
of a truck to “show their hands” was a seizure); United States
v. Bravo, 

, 1010 (9th Cir. 2002) (“Certainly
handcuffing is a substantial factor in determining whether an
individual has been arrested.”).

   [20] Numerous precedents from this court and others,
including the United States Supreme Court, make it clear that
9054                      HOPKINS v. BONVICINO
the officers’ treatment of Hopkins inside his home constituted
a seizure. There can be no doubt that the law in this respect
was clearly established prior to 2003 and thus should have
been known by a reasonable officer. See, e.g., Michigan v.
Chesternut, 

, 573 (1988); INS v. Delgado, 

, 215 (1984); 

; Chan-

. Accordingly, we affirm the district
court’s order denying Officers Buelow and Bonvicino’s
motion for summary judgment on qualified immunity grounds
with respect to Hopkins’ unlawful arrest claim. However,
because Officer Nguyen did not participate in the arrest inside
Hopkins’ home, we reverse the district court’s denial of his
motion for summary judgment with respect to this arrest. 

Part III.C.

                         B.    Citizen’s Arrest

   Hopkins also alleges that he was arrested for “hit-and-run”
without probable cause.13 This second arrest was executed
pursuant to Talib’s authority to perform a citizen’s arrest
under CAL. PENAL CODE § 837, which allows “[a] private per-
son [to] arrest another . . . [f]or a public offense committed
or attempted in h[er] presence.” The issue with respect to this
second arrest is thus whether, under the federal Constitution,
police officers are required to have independent probable
cause when effectuating an arrest authorized by a private citi-
zen.

  We first addressed this question in Arpin v. Santa Clara
Valley Transp. Agency, 

(9th Cir. 2001). In that
case, a woman who was arrested after having an argument
with a city bus driver later brought suit under § 1983. We
concluded that the “bus driver[ ] made a citizen’s arrest . . . .
and delegated to [the] [o]fficers . . . the task of taking [the
  13
    Unlike in the other claims alleged, Officer Nguyen was an integral
participant in this arrest because he provided Talib with the citizen’s arrest
form and explained the procedure to her.
                     HOPKINS v. BONVICINO                  9055
plaintiff] into 

. We upheld the grant
of summary judgment to the officers on the plaintiff’s state-
law claims for false arrest because California law explicitly
exempts officers effectuating a citizen’s arrest from civil lia-
bility. See CAL. PENAL CODE § 847. However, we reversed dis-
missal of the plaintiff’s federal claims, holding that the
officers could be liable under the Fourth Amendment because
they did not have sufficient independent probable cause to
arrest Arpin. See 

.

   [21] Given Arpin’s rule that the federal Constitution
requires police officers to have independent probable cause
when effectuating a citizen’s arrest, and taking the facts in
this case in the light most favorable to Hopkins, the
defendant-officers violated Hopkins’ constitutional rights
when they took him into custody because they did not have
probable cause to support Talib’s arrest for hit-and-run. The
hit-and-run statute on which Talib predicated her arrest con-
tains as an element that there be some damage to the vehicles
(or to some other property). See CAL. VEH. CODE § 20002;
People v. Carbajal, 

, 72 n.10 (Cal. 1995) (“The
essential elements of a violation of section 20002 [include]
that the defendant: . . . knew damage resulted from the acci-
dent . . . .”). However, Officer Nguyen personally inspected
and took photographs of the vehicles involved in the pur-
ported “accident,” and those photographs do not appear to
show any damage to the cars. “In this procedural context,
where summary judgment [is at issue], we must credit the
video evidence submitted by [the non-moving party].”
Menotti v. City of Seattle, 

, 1150 (9th Cir.
2005). Furthermore, Hopkins also asserted in his deposition
that “there was nothing wrong with either vehicle,” an asser-
tion we must take as true. If there was no damage to the cars,
then the officers did not have probable cause to believe that
a violation of § 20002 had occurred. Therefore, Hopkins has
properly alleged that the officers acted unlawfully when they
took him into custody on the basis of Talib’s citizen’s arrest
without independent probable cause.
9056                     HOPKINS v. BONVICINO
   Having concluded that the officers violated Hopkins’
rights, we must next consider whether the rule that indepen-
dent probable cause must support an officer’s effectuation of
a citizen’s arrest was clearly established at the time Hopkins
was arrested. This is a close question. We conclude that even
though Arpin was decided two years before the conduct at
issue in this case, the rule it sets forth was not clearly estab-
lished at the time of Hopkins’ arrest. Although Arpin held that
it was analyzing a citizen’s arrest when it discussed the offi-
cers’ liability under the state-law claims at issue, when the
court turned its attention to the federal claims it described the
municipal bus driver who executed the citizen’s arrest as “ac-
t[ing] ‘with the intent to assist the government in its investiga-
tory . . . purposes.’ ” 

(quoting United
States v. Attson, 

, 1433 (9th Cir. 1990)).
Accordingly, the court held that the citizen “summoned the
police . . . not for an independent purpose, but as a govern-
mental employee acting with the intent to assist the . . . Coun-
ty.” 

of this language, Arpin could reasonably be
read to suggest that the citizen bus driver was acting as an
agent of the state, and therefore not executing a true citizen’s
arrest.14 Cf. CAL. PENAL CODE § 837 (defining citizen’s arrest
as executed by a “private person”). Given this lack of clarity,
a reasonable officer might not have known that taking Hop-
kins into custody solely on the basis of the citizen’s arrest in
this case violated the Fourth Amendment.

   Since Arpin was decided, both our court and a district court
in this circuit have held in unpublished opinions that the
“teachings in Arpin . . . require police officers to conduct
additional investigation on a citizen’s arrest” in order to estab-
lish independent probable cause prior to effectuating that
  14
    The Arpin court further held that the officers in that case did not have
independent probable cause to arrest the plaintiff, but it is unclear whether
the court’s holding simply rearticulated the rule announced in Fuller v.
M.G. Jewelry, 

, 144 (9th Cir. 1991), that a statement from
an aggrieved witness is insufficient to support probable cause.
                         HOPKINS v. BONVICINO                        9057
arrest. Sin v. Crystal Park Hotel Casino, 77 F. App’x 433, 434
(9th Cir. 2003) (internal citation omitted); accord Salisbury v.
Ward, No. 06-2993-MMC, 

at
*10-11 (N.D. Cal. Dec. 19, 2006) (“[The requirement] that a
warrantless arrest . . . ‘be supported by probable cause . . . .’
applies even when the arrestee is taken into custody pursuant
to a citizen’s arrest.”). However, while unpublished opinions
“can be considered in determining whether the law was
clearly established,” Bahrampour v. Lampert, 

,
977 (9th Cir. 2004), both of these opinions were issued after
the underlying conduct in this lawsuit, which renders them
incapable of making the right at issue clearly established at
the time of the violation.

   [22] Because Arpin is unclear as to whether the bus driver
in that case was acting as a quasi-law enforcement officer or
as a private citizen in executing the arrest, we hold that the
requirement that a police officer establish independent proba-
ble cause before taking individuals into custody solely on the
basis of a citizen’s arrest was not clearly established in 2003.
Arpin’s less-than-clear reasoning makes it uncertain whether
at that time a “reasonable officer” would have known that it
was unlawful to take Hopkins into custody solely because
Talib had arrested him. It is equally uncertain whether such
an officer would have known that he needed independent
probable cause in order to do so.15 Accordingly, we hold that
  15
     Until a year prior to the time when Hopkins was arrested, a California
police officer who refused to take an individual into custody following a
citizen’s arrest could “be punished by a fine not exceeding ten thousand
dollars ($ 10,000), or by imprisonment in the state prison, or in a county
jail not exceeding one year;” that provision has since been repealed. CAL.
PENAL CODE § 142 (2001), amended by Assem. No. 1835, 2001-2002 Sess.
(Cal. 2002).
   We do not mean to imply that a conflict between an officer’s liability
under state law versus under federal law creates a lack of clearly estab-
lished federal law. Rather, when faced with a close question regarding
whether the federal law itself is clearly established, we simply note that
the fact that state law immunizes similar conduct may tend to support an
officer’s claim of qualified immunity.
9058                     HOPKINS v. BONVICINO
although Hopkins’ second arrest did indeed violate his consti-
tutional right to be free from seizure absent probable cause,
the officers are entitled to qualified immunity with respect to
that arrest.16

                        V.    Excessive Force

   Hopkins’ final claim is that the officers employed excessive
force in executing the arrest inside his house. It is clearly
established that the use of excessive force in effecting a sei-
zure violates the Fourth Amendment. See Tennessee v. Gar-
ner, 

, 8-9 (1985). The law of this circuit regarding
excessive force as it relates to the use by police officers of
drawn firearms was established by the en banc court in Robin-
son v. Solano County, 

(9th Cir. 2002) (en
banc). In that case, we held that “pointing a gun to the head
of an apparently unarmed suspect during an investigation can
be a violation of the Fourth Amendment, especially where the
individual poses no particular danger.” 

In Robin-
son, the court held that a constitutional violation had occurred
where the officers pointed their guns at the plaintiff and “[t]he
crime under investigation was at most a misdemeanor[,] the
suspect was apparently unarmed and approaching the officers
in a peaceful way[,] [t]here were no dangerous or exigent cir-
cumstances apparent at the time of the detention, and the offi-
cers outnumbered the plaintiff.” 

   [23] Taking the facts in the light most favorable to the
plaintiff, it is clear that this case is indistinguishable from
Robinson. Officer Bonvicino stated in his declaration that, at
least as of the time Hopkins got up from the bedroom floor,
he knew that Hopkins “was not a threat to officer safety.”
  16
     Our holding therefore excuses Officer Nguyen from all liability,
including liability for the excessive force claim, and dismisses him as a
defendant in this case. Officers Bonvicino and Buelow, however, are not
entitled to qualified immunity with respect to either the warrantless entry
into Hopkins’ home or the warrantless arrest inside his home.
                    HOPKINS v. BONVICINO                 9059
However, Officer Buelow makes clear in his declaration that
he did not holster his weapon until after Hopkins was hand-
cuffed, sometime after Officer Bonvicino described Hopkins
as nonthreatening. Furthermore, the facts in the record,
including the officers’ own testimony that their reason for
forcefully entering Hopkins’ home was that they suspected he
was suffering from a medical emergency, suggest that they
were fully aware at all times that Hopkins did not pose a
threat to anyone. As to the other facts described in Robinson,
there is no dispute that the officers here outnumbered Hop-
kins, that he was unarmed, and that any putative crime the
officers might have been investigating was a misdemeanor.
Because Robinson was the law of this circuit at the time the
officers arrested Hopkins, it was clearly established that the
force they used was excessive. Accordingly, the district
court’s denial of summary judgment on this ground with
respect to Officers Bonvicino and Buelow is affirmed. The
district court’s grant of summary judgment on this claim in
favor of Officer Nguyen, who did not participate in the arrest
inside Hopkins’ home, is also affirmed. 

note 16 

Part III.C.

                         Conclusion

   The district court’s denial of summary judgment with
respect to Officers Bonvicino and Buelow is AFFIRMED
except with respect to the citizen’s arrest part of the
warrantless-arrest claim. The grant of summary judgment in
favor of Officer Nguyen with respect to the excessive force
claim is also AFFIRMED. The denial of summary judgment
to Officer Nguyen with respect to the unlawful warrantless
entry and unlawful arrest claims is REVERSED. The case is
REMANDED for further proceedings consistent with this
opinion.

 AFFIRMED in part, REVERSED in part, and
REMANDED.