PUBLISHED

UNITED STATES COURT OF APPEALS
                FOR THE FOURTH CIRCUIT


UNITED STATES OF AMERICA,               
                 Plaintiff-Appellant,
                 v.                             No. 03-4403
DAVID LYNN HATFIELD,
              Defendant-Appellee.
                                        
           Appeal from the United States District Court
      for the Southern District of West Virginia, at Beckley.
               David A. Faber, Chief District Judge.
                           (CR-02-219)

                      Argued: January 23, 2004

                      Decided: April 23, 2004

    Before WIDENER, MOTZ and GREGORY, Circuit Judges.



Vacated and remanded by published opinion. Judge Widener wrote
the opinion, in which Judge Motz and Judge Gregory concurred.


                            COUNSEL

ARGUED: Joshua Clarke Hanks, Assistant United States Attorney,
Charleston, West Virginia, for Appellant. Jonathan David Byrne,
Legal Research and Writing Specialist, OFFICE OF THE FEDERAL
PUBLIC DEFENDER, Charleston, West Virginia, for Appellee. ON
BRIEF: Kasey Warner, United States Attorney, Charleston, West
Virginia, for Appellant. Mary Lou Newberger, Federal Public
Defender, George H. Lancaster, Jr., Assistant Federal Public
Defender, Charleston, West Virginia, for Appellee.
2                     UNITED STATES v. HATFIELD
                              OPINION

WIDENER, Circuit Judge:

  This is a case of an unannounced entry under the Fourth Amend-
ment.

   In this criminal case, the United States appeals from the district
court’s order excluding from evidence a pistol found in the pocket of
the defendant upon his arrest on an unrelated charge by Wyoming
County, West Virginia deputy sheriffs. The defendant was indicted
for possession of the pistol by a convicted felon under 18 U.S.C. §§
922(g)(1) and 924(a)(2). The district court, however, concluded that
the deputies violated the defendant’s Fourth Amendment rights. The
government appeals, and we vacate the order of the district court.

                                   I.

   During the evening hours of January 3, 2002, Wyoming County
deputies Donald Cook and Jerry McClain went to David Lynn Hat-
field’s house near Baileysville, West Virginia, in order to serve a state
felony warrant for Hatfield’s arrest. Another deputy had originated
the warrant, which was for the delivery of a controlled substance. The
deputies, both in uniform, arrived at Hatfield’s residence at about 8:00
p.m. in a marked patrol vehicle. Upon reaching the residence, Deputy
McClain knocked on the door of Hatfield’s home.

   At the suppression hearing in the district court, Deputy McClain
testified that after he knocked, "[he] heard a voice say, ‘[t]he door is
open; come on in.’" McClain recognized the voice as that of Hatfield
from three or four previous conversations over the years when he had
come to know Hatfield, whose voice was "a little different from oth-
ers, and [he] could tell [Hatfield’s] voice." Upon hearing Hatfield’s
statement, Deputies McClain and Cook "opened the door and went on
in" Hatfield’s residence and immediately saw Hatfield on a couch
about ten feet in front of them. Deputy Cook’s testimony corroborated
McClain’s version of events. Neither Cook nor McClain announced
their presence as law enforcement officers prior to entering Hatfield’s
residence. Deputy Cook did testify that he saw Hatfield, apparently
through the door prior to getting inside.
                       UNITED STATES v. HATFIELD                         3
   After entering Hatfield’s residence, the two deputies approached
Hatfield, and McClain informed Hatfield that he and Cook had a war-
rant for Hatfield’s arrest for delivery of a controlled substance. As he
approached, McClain asked Hatfield if Hatfield had any guns on his
person. Hatfield stated that he had a gun in his inside coat pocket.
McClain patted Hatfield down and discovered a gun in Hatfield’s
inside coat pocket. The deputies also found prescription drug bottles
in Hatfield’s jacket pocket and pants pocket. Upon recovering the
gun, an H & K .40 caliber pistol, the deputies placed Hatfield under
arrest and handcuffed him, and Deputy McClain took Hatfield to the
patrol vehicle outside the residence. Two other individuals were in
Hatfield’s residence at the time the deputies arrived. As soon as Hat-
field was arrested, these two individuals left Hatfield’s residence.

   Deputy Cook remained in the residence for fifteen minutes after
McClain escorted Hatfield to the patrol vehicle. Cook retrieved only
other items that had been discovered in plain view or during the
search of Hatfield’s person, including Hatfield’s prescription drug
bottles and a small amount of marijuana that was found on the coffee
table after the deputies entered the residence. Deputy Cook did search
each room in the residence, but he testified that he only looked into
each room and did not open drawers or conduct an extensive search.
In the kitchen, he found and seized various unmarked prescription
bottles and 50 to 60 pills.

   At the hearing in the district court, Hatfield testified that he did not
say "come on in" to the deputies. Hatfield did state, however, that
after the deputies entered his trailer, they did tell him that he had
either said "come — the door is open," or "come on in." Hatfield also
testified that he could not be certain of what the deputies said to him.
Hatfield has a prior state felony conviction for possession of a con-
trolled substance with intent to deliver.

                                    II.

   A federal grand jury indicted Hatfield on the charge of being a
felon in possession of a firearm, the .40 caliber H & K pistol, in viola-
tion of 18 U.S.C. § 922(g)(1). Hatfield filed a motion to suppress any
evidence seized by the deputies after their entry into Hatfield’s resi-
dence. In his motion, Hatfield contended that the deputies violated his
4                     UNITED STATES v. HATFIELD
constitutional rights by failing to identify themselves as law enforce-
ment officers before entering his residence. The district court held a
hearing on the motion to suppress on February 11, 2003.

   Following a suppression hearing, the district court made the fol-
lowing written findings of fact, which are not clearly erroneous and
are supported by the record:

                        I. Findings of Fact

    On the evening of January 3, 2002, Wyoming County Sher-
    iff’s Deputies Cook and McClain went to the residence of
    the defendant in Wyoming County, West Virginia, to exe-
    cute a state felony warrant for the arrest of the defendant.
    Upon their arrival, the deputies knocked on the door of the
    defendant’s residence but did not announce their identities
    or purpose, although no exigent circumstances prevented
    them from doing so. A male voice from inside the defen-
    dant’s residence replied to the knock, "The door is open;
    come on in." Deputy McClain, who had spoken to the
    defendant several times in the past, recognized the voice
    coming from the defendant’s residence as the voice of the
    defendant. This invitation to enter was a voluntary act upon
    the defendant’s part.

    Still without announcing their identities, purpose, or author-
    ity the deputies opened the closed but unlocked door of the
    defendant’s residence and entered, finding the defendant
    seated upon his couch in plain view of the doorway. After
    entering the residence, the deputies explained to the defen-
    dant that they held a warrant for his arrest. Prior to advising
    the defendant of his Miranda rights, Deputy McClain asked
    the defendant if he possessed any weapons. The defendant
    replied that he had a gun in his coat pocket. The deputies
    then conducted a search of the defendant’s person and found
    in his coat a .40 caliber handgun. That handgun forms part
    of the evidentiary basis for the indictment in this case,
    which charges the defendant with being a felon in posses-
    sion of a firearm. (Footnote omitted.)
                      UNITED STATES v. HATFIELD                        5
   On April 11, 2003, the district court granted Hatfield’s motion to
suppress. United States v. Hatfield, No. 5:02-00219-01, slip. op. (S.D.
W. Va. Apr. 11, 2003). The district court concluded that what is
known as the "knock-and-announce" rule in Richards v. Wisconsin,

, 387 (1997), and Wilson v. Arkansas, 

, 934
(1995), applied to the deputies’ conduct. Under Richards and Wilson,
under some circumstances, law enforcement officers must knock and
announce their presence before attempting forcible entry of a dwell-
ing. 

; Wilson 

. The district
court noted that the knock-and-announce rule allows law enforcement
officers to forcibly enter a dwelling without knocking and announcing
their presence only "under circumstances presenting a threat of physi-
cal violence" or "where police officers have reason to believe that evi-
dence would likely be destroyed if advance notice were given."
Hatfield, slip op. at 4 (quoting 

). The district
court determined that the government failed to produce any evidence
that either of the two exigent circumstances were present at the time
Deputies McClain and Cook entered Hatfield’s residence. (J.A. 73)

   The district court next determined that Hatfield’s statement "come
on in" did not manifest consent sufficient to allow the deputies to
enter the house. According to the district court, Hatfield’s statement
was given in response to a knock only, not a knock and an announce-
ment that law enforcement officers were at his door. If it upheld the
entry, the district court reasoned, it would be creating an exception to
the knock-and-announce rule that would transform the rule from
knock and announce to "knock." (J.A. 74-75)

   The district court concluded that Hatfield’s invitation to the depu-
ties to enter the residence was not an "intervening act of free will."
(citing Wong Sun v. United States, 

(1963)). Under the
district court’s analysis, the invitation was not intervening because it
occurred after the deputies knocked on the door but before the depu-
ties completed the constitutional violation by opening Hatfield’s door
and entering the residence. Based on the timing of the entry, the dis-
trict court deduced that "a Wong Sun analysis is inapposite herein and
may not serve to remove the taint from the challenged evidence."
(J.A. 75) The district court decided that the firearm found on Hatfield
was obtained through a violation of Hatfield’s Fourth Amendment
6                     UNITED STATES v. HATFIELD
Constitutional rights and ordered the firearm excluded from evidence.
(J.A. 76)

                                   III.

   On May 9, 2003, the government filed its notice of appeal with the
district court. While the notice of appeal was timely under Rule
4(b)(1)(B) of the Federal Rules of Appellate Procedure, the govern-
ment did not file the certification required by 18 U.S.C. § 3731 with
the district court until January 16, 2004, just one week before the case
was argued in this court. Section 3731 of Title 18 of the United States
Code provides, in pertinent part:

    An appeal by the United States shall lie to a court of appeals
    from a decision or order of a district court suppressing or
    excluding evidence . . . not made after the defendant has
    been put in jeopardy and before the verdict or finding on an
    indictment or information, if the United States attorney cer-
    tifies to the district court that the appeal is not taken for pur-
    pose of delay and that the evidence is a substantial proof of
    a fact material in the proceeding.

18 U.S.C. § 3731. The assistant United States attorney who presented
the government’s oral argument stated in oral argument that the fail-
ure to file the certification required by § 3731 was a "regretful over-
sight."

   On July 15, 2003, Hatfield filed a motion to dismiss the govern-
ment’s appeal in this court. In his motion, Hatfield argues that the
government’s appeal should be dismissed because the failure of the
United States to file the certification has prejudiced him. The specific
prejudices, according to Hatfield, are the continued pretrial release
restrictions and the burden of an impending trial.

   In its response, the United States contends that the certification
requirement is discretionary and not jurisdictional. The United States
also argues that the nature of the district court’s opinion and order
granting Hatfield’s motion to suppress, in particular the language in
its opinion stating that the ruling "is essentially a death knell for the
                      UNITED STATES v. HATFIELD                        7
government’s case in this matter," is proof that the evidence sup-
pressed is substantial proof of a material fact. The United States con-
tends that its timely notice of appeal and the immediate initiation of
internal procedures to gain permission from the Solicitor General to
pursue this appeal are evidence that this appeal is not taken for the
purpose of delay.

    The United States is correct that the certification requirement in
§ 3731 is not jurisdictional. In re Grand Jury Subpoena, 

, 337 (4th Cir. 1999), so holds. Our holding with respect to juris-
diction in In re Grand Jury Subpoena is in accordance with other cir-
cuits’ case law. See United States v. Bookhardt, 

, 562
(D.C. Cir. 2002); United States v. Smith, 

, 578-80 (6th
Cir. 2001); United States v. Romaszko, 

, 760 (2d Cir.
2001) (per curiam); United States v. Gantt, 

, 997 (9th
Cir. 1999); United States v. Salisbury, 

, 1206 (11th Cir.
1998); United States v. Bailey, 

, 1163 (7th Cir. 1998);
United States v. Welsch, 

, 224 (10th Cir. 1971). In the
case of a delayed filing, the appellate court may, within its discretion,
hear the case despite the irregularity in the perfection of the appeal.
See 

("[A] failure to timely file a certificate is
an irregularity in perfecting the appeal."); see also Fed. R. App. P.
3(a)(2) ("An appellant’s failure to take any step other than the timely
filing of a notice of appeal does not affect the validity of the appeal,
but it is ground only for the court of appeals to act as it considers
appropriate, including dismissing the appeal.").

   In weighing the equities in a case where the certification was not
filed as prescribed in § 3731, courts of appeals have utilized several
factors including the date the certificate was filed, the reason for the
lateness in filing the certificate, whether the government did engage
in a conscientious pre-appeal analysis, whether the government
acknowledges the importance of the certification requirement, any
prejudice to the defendant, whether the appeal concerns issues that
require appellate clarification, and whether the appeal should be heard
in the interests of justice. See 

(listing factors
considered by courts of appeals in exercising their discretion to hear
the appeal). Analyzing these factors, although all do not favor the
government, we believe the equities of the case favor the United
States. It is not disputed that the government did undertake the
8                     UNITED STATES v. HATFIELD
required process to obtain permission from the Solicitor General to
pursue this appeal. The attorney for the government also candidly
admitted the oversight which led to the delay in filing the certifica-
tion. More importantly, the issue raised on appeal is a novel legal
issue and one which will further delineate the boundaries imposed by
the Fourth Amendment on searches and seizures. Also weighing
heavily in favor of entertaining the government’s appeal is the fact
that, unlike other circuits, before today we had not yet fully explicated
the importance of the certification requirement, and the grave conse-
quences resulting from the government’s failure to timely file. And
finally, whatever prejudice the defendant suffered from pre-trial
release, it was not substantial enough to outweigh these other factors.

   The equities of the case favoring the government, under the author-
ity of F.R.A.P. 3(a)(2), we exercise our discretion, deny the defen-
dant’s motion to dismiss the appeal, and decide the case on the
merits.* In doing so, however, we take this opportunity to emphasize
the importance of the certification requirement and to serve notice on
the government that future failures to timely file will not be taken
lightly.

                                  IV.

   In United States v. Cephas, 

, 493 (4th Cir. 2001), we
explained that "[a] voluntary response to an officer’s knock at the
front door of a dwelling does not generally implicate the Fourth
Amendment." The factual scenario in Cephas is quite similar to the
facts of the instant case. A passerby informed a Richmond, Virginia
police sergeant that he had just come from an apartment where a 14-
year-old girl was smoking marijuana with a man named Cephas. The
passerby gave the officer the location of the apartment, and the officer
went to the address to investigate. The officer knocked on the first
door at the residence, a house divided into several apartments, and a

  *The Fifth, Tenth, and Eleventh Circuits have dismissed, not on juris-
dictional grounds, appeals by the government in cases where the govern-
ment failed to comply with § 3731. See United States v. Salisbury, 

, 1207 (11th Cir. 1998); United States v. Carillo-Bernal, 

, 1497 (10th Cir. 1995); United States v. Miller, 

,
875-76 (5th Cir. 1992). But see the string citation, 

.
                      UNITED STATES v. HATFIELD                       9
woman answered the door, which opened into a common area. The
officer inquired of the woman about Cephas, and she told him that
Cephas rented the apartment at the top of the stairs to the right. The
officer went to the door described by the woman and knocked. A
man, later determined by the district court to be Cephas, opened the
door.

   Through the opened door, the officer could see a young girl sitting
in the apartment and could smell a strong odor of marijuana. The offi-
cer asked Cephas if he could enter the apartment and speak with
Cephas, but Cephas attempted to slam the door on the officer. The
officer then forced his way into the apartment. Upon entry, the officer
discovered eight or nine people in the apartment and what he believed
to be a marijuana "roach" in the ashtray. Other law enforcement offi-
cers arrived, and they conducted a protective sweep of the apartment
and patted down the persons found in the apartment. The officers
obtained a search warrant and searched the apartment. Either during
the search of the apartment pursuant to the search warrant or during
the protective sweep, officers discovered "cigar blunts" containing
marijuana, individually wrapped packages of crack cocaine, a .22 cal-
iber pistol, a shotgun with no serial number, and a police scanner.
Cephas was arrested, and a grand jury later indicted Cephas for pos-
session of cocaine base, possession of marijuana, and three possession
of firearms charges.

  Cephas sought to suppress the evidence seized by the police on the
basis that it was seized in violation of his Fourth Amendment rights.
The district court granted Cephas’s motion to suppress the evidence.
We reversed on the grounds that Cephas voluntarily opened his door
and allowed the officer to view the illegal activities occurring inside,
namely the presence of a young girl in a room smelling of marijuana.
We explained that

    [T]here is no evidence that Cephas’s act of initially opening
    his door to [the officer] was anything but voluntary. . . .
    [The officer] testified that he next knocked on Cephas’s
    door and the door then opened. Nothing in the record sug-
    gests the officer used his authority to command that the door
    be opened. Indeed, the district court found that Cephas was
10                    UNITED STATES v. HATFIELD
     not aware that it was a police officer who was knocking at
     his door until the door was already 

.

   In its opinion in the case at hand, the district court determined that
the Supreme Court’s opinions in Richards and Wilson established the
rule that "any forcible entry into a dwelling must be preceded by both
a knock and a notice of identity and authority unless it would be
unreasonable for the government agents to announce their presence."
(citing 

; 

). The
exceptions to this rule occur when government agents encounter cir-
cumstances that present a threat of physical violence and when evi-
dence may be destroyed if agents announce their presence. 

(citing 

); see also United
States v. Wardrick, 

, 452 (4th Cir. 2003) ("We have rec-
ognized that, under appropriate exigent circumstances, strict compli-
ance with the knock and announce requirement may be excused.").
Applying the knock-and-announce rule in the instant case, the district
court determined that the government failed to prove that Deputies
Cook and McClain believed that Hatfield would present a physical
danger to the officers or others or that he would destroy any potential
evidence. Accordingly, the district court concluded that the deputies
violated Hatfield’s Fourth Amendment rights by entering Hatfield’s
residence without first announcing their presence and authority.

   The district court next determined that Hatfield’s statement "[t]he
door is open; come on in" did not rise to the level of consent suffi-
cient to validate a violation of a person’s Fourth Amendment rights.
The Supreme Court in Schneckloth v. Bustamonte, 

, 248-
49 (1973), held that consent, if voluntarily given in the absence of
duress or coercion, may serve as the basis for government agents to
conduct a search which would not otherwise be authorized by the
Fourth and Fourteenth Amendments. The question of whether the
consent was voluntary is determined from the totality of all the cir-

, 249. In declining to apply the Court’s
reasoning in Bustamonte to the case at bar, the district court stated
that "the consent issue is in some ways a red herring" because Hat-
field stated his consent to enter his dwelling to whoever was knocking
at his door after only hearing a knock, not a knock and an announce-
                      UNITED STATES v. HATFIELD                       11
ment of law enforcement authority. The district court reasoned that by
accepting the consent argument advanced by the government it would
create "an exception that turns the knock and announce rule into the
knock rule." We review the district court’s legal conclusions related
to search and seizure issues de novo. United States v. Rusher, 

, 873 (4th Cir. 1992).

    We do not consider consent to be a red herring; it is the principal
issue in the case. Hatfield, in his dwelling and free from any coercion
or duress, heard a knock at the door and unequivocally stated "[t]he
door is open; come on in." By his statement, Hatfield gave consent
to enter to whoever was standing at his door. The persons knocking
at the door could have been pollsters, salesmen, or, as in this case,
officers of the law. See United States v. Taylor, 

, 909 (4th
Cir. 1996) ("‘Absent express orders from the person in possession
against any possible trespass, there is no rule of private or public con-
duct which makes it illegal per se, or a condemned violation of the
person’s right of privacy, for any one openly and peaceably . . . to
walk up the steps and knock on the front door of any man’s ‘castle’
. . . whether the questioner be a pollster, a salesman, or an officer of
the law.’") (quoting Davis v. United States, 

, 303 (9th
Cir. 1964)). Hatfield’s statement authorized the persons knocking at
his door to "come on in." Thus, when the deputies opened Hatfield’s
unlocked door, they had been authorized to do so, just as Cephas vol-
untarily opened his door to the officer who knocked on his door. See

. They did not forcibly enter Hatfield’s dwell-
ing.

   By its terms, the knock-and-announce rule applies when law
enforcement officers attempt a forcible entry into a dwelling. See

. Hatfield’s consent, transmitted to Deputies
Cook and McClain through his statement that "[t]he door is open;
come on in," made the deputies’ entrance into Hatfield’s dwelling a
permissible one. There is no distinction between a person voluntarily
opening the door to his dwelling after hearing a knock and without
ascertaining the identity of the person knocking and a person who,
after hearing a knock and failing to ascertain the identity of the person
knocking, speaks to the person knocking and tells the person "[t]he
door is open; come on in."
12                    UNITED STATES v. HATFIELD
   We conclude that Hatfield’s statement to the deputies was volun-
tary and amounted to an invitation to them to enter his dwelling
regardless of the fact that Hatfield did not know who was knocking
at his door. See 

(noting that a defendant can
voluntarily open a door to his residence even if he does not know the
identity of the person knocking on his door). Hatfield’s consent ren-
ders the deputies’ entrance into his dwelling a permissible one, and
the knock-and-announce rule does not apply to bar the introduction
into evidence of the .40 caliber H & K pistol obtained in this reason-
able unannounced entry. We do not agree with the district court that
there was any taint to dissipate under Wong Sun; the entry being rea-
sonable, there is no taint to dissipate.

  Finally, we explain that we do not create an exception to the
knock-and-announce rule. Our warrant does not extend so far. We
have, however, engaged in the task assigned to us by the Court in
Richards and Wilson, at 936, as "left to the lower courts . . . of deter-
mining the circumstances under which an unannounced entry is rea-
sonable under the Fourth Amendment." Richards, 

and
387. We are of opinion and hold that the unannounced entry in this
case was reasonable and not in violation of the Fourth Amendment.

                                   V.

   Hatfield argues that we should affirm the order of the district court
for the alternate reason that the deputy sheriffs in this case seized
more than 50 items in what he terms an illegal general search. None
of any such items was offered or received as evidence in this case,
and we reject his contention. The pistol, for the possession of which
Hatfield was indicted, and the object of the suppression motion, was
delivered by Hatfield to the officers upon their simple request and not
as a result of any general search, assuming for argument the same was
undertaken. The order of the district court appealed from is accord-
ingly vacated, and the case is remanded for action not inconsistent
with this opinion.

                                        VACATED AND REMANDED