In the
 United States Court of Appeals
               For the Seventh Circuit
                          ____________

No. 03-3175
DAVID HAYWOOD,
                                                 Plaintiff-Appellant,
                                 v.

CITY OF CHICAGO, et al.,
                                             Defendants-Appellees.

                          ____________
         Appeal from the United States District Court for the
           Northern District of Illinois, Eastern Division.
           No. 01-C-3872—Matthew F. Kennelly, Judge.
                          ____________
     ARGUED MARCH 30, 2004—DECIDED AUGUST 10, 2004
                          ____________



  Before POSNER, RIPPLE, and MANION, Circuit Judges.
  POSNER, Circuit Judge. David Haywood brought suit for
damages under 42 U.S.C. § 1983 against the City of Chicago
and two of its police officers, charging false arrest and
detention in violation of his federal constitutional rights. He
appeals from the grant of the defendants’ motion for
summary judgment, and so we construe the facts as favor-
ably to him as the record permits, simplifying them where
possible.
  When arrested, Haywood was employed by a pawnshop
as an armed security guard. He was just beginning his
commute to work from his home on Chicago’s south side
2                                                No. 03-3175

one day when the defendant police officers, Maras and
Marozas, acting on a tip that Haywood was armed, pulled him
over. They asked him where he was going; he explained that
he was on his way to the pawnshop. They noticed that he
had two guns with him; he told them he had papers that
proved he was authorized to carry them and he showed
them the papers. The papers included a firearm owner’s
identification card and a “blue card,” which certifies eligi-
bility to work for a licensed security agency, 225 ILCS 446/80
(2002), reenacted at 225 ILCS 447/35-30, but did not include
either a Chicago gun registration certificate or a “tan card,”
which certifies that the cardholder, being employed by a
licensed security agency (which Haywood probably was not,
although this is uncertain) and having received firearms
training, may carry a weapon while working or commuting.
225 ILCS 446/185(a), (b), (e) (2002), reenacted at 225 ILCS
447/35-35(a) through (d); 720 ILCS 5/24-2(a)(5). He also had
a memo from the police department stating that individuals
licensed by the state under the Private Detective, Private
Alarm, Private Security, and Locksmith Act of 1993, 225
ILCS 446/1 et seq. (2002), do not have to register their
weapons; Haywood probably was not licensed, but again
this is uncertain. The officers arrested him, though appar-
ently only because he failed to show them a Chicago gun
registration certificate, the failure being “presumptive evi-
dence that he [was] not authorized to possess such firearm.”
Chicago Municipal Code § 8-20-150. The officers seem to
have been unaware that he should have had a tan card as
well.
  Haywood was jailed, and the next day taken before a state
court judge for a probable-cause hearing. No one testified at
the hearing. The only evidence submitted (besides the arrest
report, on which the defendants no longer place any weight)
to persuade the judge to find probable cause to detain
Haywood was a complaint charging him with knowingly
No. 03-3175                                                   3

carrying a concealed, loaded firearm without a license, in
violation of 720 ILCS 5/24-1.6(a)(1), (3)(A). He was not
charged with having failed to register his guns; they may
have been registered, though this is uncertain and he hadn’t
had a registration certificate with him when he was arrested.
  In the space in the complaint for the “complainant’s sig-
nature” appeared Officer Marozas’s name, but in fact Maras
had written the complaint and had signed Marozas’s name
to it. There was no indication of this anywhere in the docu-
ment, however; nor did the prosecutor mention the fact, of
which she may have been unaware, at the hearing. In the
place in the complaint for a judge’s or court clerk’s signa-
ture (the “jurat”—Latin for “he swears”), attesting that
Marozas had both signed the complaint and sworn to the
truth of its contents, Maras had written and signed the name
of still another police officer, Brumley. Chicago police
officers are eligible to sign the jurat because they are
appointed as deputy clerks of the Cook County circuit court.
But Brumley, even if he’d signed the jurat, could not have
truthfully sworn that Marozas had signed the complaint,
because he hadn’t.
  On the basis of the complaint, the judge ruled that there
was probable cause to hold Haywood, and it took the latter
10 days to raise bail money and get out of jail. The charge
against him was later dropped. Haywood contends, and for
purposes of ruling on summary judgment we must assume,
that until the defendants began to prepare their defense
against his suit neither the prosecutor, nor the police officers
who had arrested Haywood, were aware that his failure to
have a tan card was a crime.
  He contends that the arrest violated his Fourth Amendment
rights because it was not based on probable cause to believe
he’d violated any law. The defendants counter with the
principle that if arresting officers know facts that indicate
4                                                 No. 03-3175

that the person they arrested has committed a crime, the fact
that they didn’t know the legal significance of those facts
does not invalidate the arrest. E.g., United States v. Reed, 

, 462-63 (7th Cir. 2003); Biddle v. Martin, 

, 676-77 (7th Cir. 1993); Richardson v. Bonds, 

,
1430-31 (7th Cir. 1988); Bingham v. City of Manhattan Beach, 

, 950-53 (9th Cir. 2003). After all, they are not
lawyers, and to award a criminal damages because, though
he engaged in conduct that any legally trained observer
would have noticed was criminal, he had the good fortune
to be arrested by officers who didn’t have the requisite
training and so didn’t know he had indeed committed a
crime, would be to turn their mistake into his windfall.
  The defendants point to two facts known (though their
legal significance probably was not) to the officers that
demonstrate probable cause to arrest Haywood. The first is
that he was arrested at about 7:45 a.m., and when one of the
officers called the pawnshop to verify Haywood’s em-
ployment the person who answered the phone told him that
Haywood’s starting time was 9 a.m. It is illegal for a
security guard to carry a weapon to and from work unless
“such commuting is accomplished within one hour from
departure from home or place of employment, as the case
may be.” 720 ILCS 5/24-2(a)(5). So if Haywood, having left
his home sometime before 7:45 (in fact, he testified, at 7:39),
would not arrive at work until 9, he would violate the one-
hour rule. But the fact that Haywood’s official start time is
9 a.m. is weak evidence that he wasn’t planning to arrive
until then. To be on time, one has to plan to arrive somewhat
early (especially if the employee is expected to change into a
uniform, or make other preparations, at his place of employ-
ment before actually beginning to work)—and in fact
Haywood testified (and had told the arresting officers) that
he was due at the pawnshop by 8:45. If that was the expecta-
tion, to satisfy it he would have to arrive a few minutes
No. 03-3175                                                      5

before then. If he arrived at 8:39, he would have been
commuting for only an hour.
   So there was only slight reason to think he was going to
violate the one-hour rule. This was provided the police be-
lieved that he was expected to show up at work 15 minutes
before his official starting time. But though they didn’t have
to believe him, they didn’t call the pawnshop and learn
about Haywood’s 9 a.m. start time until after they had
arrested him. So it was not a fact that they knew at the time
of his arrest; and “what an arresting officer does not know
is inadmissible to show that he had probable cause for the
arrest—otherwise hindsight would validate every arrest of
a person who turned out to be a criminal.” Villanova v. Abrams,

, 799 (7th Cir. 1992); see also Beck v. Ohio, 

, 91 (1964); Thompson v. Wagner, 

, 934-35
(7th Cir. 2003); United States v. Copeland, 

, 592-93
(6th Cir. 2003).
  We needn’t resolve the one-hour issue, however, because
there is still the missing tan card and its absence clearly
created probable cause to arrest Haywood. Of course, not
knowing that Haywood should have had a tan card, it is
only in an attenuated sense that the officers can be said to
have “known” that he did not have it. But he purported to
exhibit to them the papers that authorized him to carry a
gun, and a police officer who knew the law would have
seen that the array was incomplete. See People v. Mourecek,

, 845-46 (Ill. App. 1991).
  So Haywood was arrested lawfully. But he could not, con-
sistent with the Fourth Amendment, be continued in custody
beyond 48 hours (with inapplicable exceptions) unless a
judicial officer determined that there was probable cause to
believe that he had committed a crime. County of Riverside v.
McLaughlin, 

, 56-57 (1991); Chortek v. City of Milwau-
kee, 

, 746 (7th Cir. 2004); Kyle v. Patterson, 

                                                No. 03-3175

695, 696 (7th Cir. 1999); Luck v. Rovenstine, 

, 324
(7th Cir. 1999). The defendants argue, rather desperately as
it seems to us, that although an arrest warrant may not be
issued except on the basis of a sworn affidavit or other
sworn testimony (the Fourth Amendment is explicit that
“no Warrants shall issue, but upon probable cause, sup-
ported by Oath or affirmation”), a person may be detained
indefinitely on the basis of an unsworn complaint; that
anyway the complaint purportedly signed by Marozas was
sworn, albeit falsely, or at least that “the complaint purports
to be signed under penalty of perjury” (emphasis
added)—whatever that means; that Marozas and Brumley
consented to have their names forged; and that the practice
of misrepresenting the names of the signing officer and notary
is merely a “procedural shortcut” made “in the service of
convenience.” At oral argument the City of Chicago’s lawyer,
representing all three defendants, conceded the impropriety
of the practice. But the defendants’ brief states only that it
might be “preferable for the officer signing for his partner
to place his own initials next to the signature,” and we are
reluctant to give binding effect to a concession made in the
heat of argument.
   The officers’ depositions described the practice of signing
someone else’s name (without disclosure) to a criminal com-
plaint as common, and there is no contrary evidence. If it is
common enough to be described as customary—as a
practice that the City has so far condoned as to make it a
policy—this would be sufficient to defeat any argument that
if the practice is unconstitutional the City nevertheless, by
virtue of the doctrine of Monell v. Department of Social
Services, 

, 694-95 (1978), cannot be held liable for
it. See Palmer v. Marion County, 

, 594-95 (7th Cir.
2003); Jackson v. Marion County, 

, 152 (7th Cir.
1995); Bielevicz v. Dubinon, 

, 849-52 (3d Cir.
No. 03-3175                                                      7

1990). We need not decide, as the City does not argue that
it isn’t liable even if the practice is unconstitutional.
  Nor do the officers argue qualified immunity in this court.
Rather they argue that since an arrest is commonly made on
the basis of an unsworn statement, such as an informer’s tip,
“a judicial officer should be no less entitled to rely on
unsworn evidence, including the statements of police offi-
cers, when assessing probable cause to arrest.” Not only is
there a difference between evidence that the judicial officer
knows is unsworn and evidence that he is fraudulently in-
duced to believe has been sworn, but the argument contradicts
the defendants’ position that a falsely sworn statement is the
equivalent of a properly sworn statement.
   Their further argument—that because the Fourth
Amendment mentions “Oath or affirmation” only in connec-
tion with the issuance of warrants, less evidence is required
to detain a person indefinitely than to arrest him even
though the curtailment of liberty is greater—is wooden, and
was rejected by the Supreme Court in Gerstein v. Pugh, 

, 113-14 (1975). The Court noted that “the conse-
quences of prolonged detention may be more serious than
the interference occasioned by arrest” and therefore “the
Fourth Amendment requires a judicial determination of
probable cause as a prerequisite to extended restraint of
liberty following arrest.” 

see also Villanova v.

, 972 F.2d at 796-98; United States v. Chaidez, 

, 1196-98 (7th Cir. 1990). Since all that is required is a
determination of probable cause, we need not make a fetish
of sworn testimony; one can imagine cases in which its
absence would not invalidate a finding of probable cause. It
is true that the Fourth Amendment requires that warrants
be on oath, but warrants are issued in ex parte proceedings,
whereas a suspect might confess his crime in open court at
8                                                   No. 03-3175

his probable-cause hearing, and that would be an even
stronger basis for continued detention than a sworn com-
plaint.
   The only basis for a finding of probable cause on which
the state relies in this case, however, was a falsely sworn
complaint whose falsity was, so far as appears, unknown to
the judge at the probable-cause hearing. (Compare United
States v. Causey, 

, 1343-44 and n. 1 (7th Cir. 1993),
where the judge was informed that a pseudonym had been
used in an affidavit to protect the identity of a confidential
informant.) Apparently Marozas was in court as well as
Maras, though this is not entirely clear. But if so he didn’t
testify, and given the complaint the judge had no reason to
question him and did not. On its face it looked like a com-
plaint signed by an officer under penalty of perjury if he
was lying—indeed, signed by the officer who had accompa-
nied the prosecutor to court—with his signature duly
notarized so that he couldn’t later, if charged with perjury,
deny that it was his signature. It is the prospect (remote as
it may be) of prosecution for perjury, plus whatever slight
moral pressure the taking of a solemn oath may still exert,
that furnishes the rationale for preferring sworn to unsworn
testimony. The prospect and pressure were weakened in
this case by the forgeries. Even if Maras was authorized to
sign Marozas’s name, if it turned out that the complaint was
perjurious Marozas, who neither drafted the complaint
(Maras did) nor signed it, could not be prosecuted, unless
perhaps he authorized Maras to sign his name without
disclosure that it wasn’t really Marozas’s signature; in that case
he could probably be prosecuted for subornation of perjury.
720 ILCS 5/32-3. Maras could be prosecuted for perjury; he
presumably would be estopped by his fraud to deny that the
false signature was a representation made “under Oath or
affirmation.” 720 ILCS 5/32-2; People v. Dinger, 

, 1350 (Ill. App. 1982); People v. O’Neal, 

,
No. 03-3175                                                    9

284 (Ill. App. 1976); United States v. Brooks, 

(8th Cir. 2002). That may be why the defendants latch on to
the fact that the complaint was sworn, though by whom,
exactly, is obscure. But they do not concede that anyone
could be prosecuted for perjury should the contents of such
a complaint be found to be perjurious, and certainly such a
prosecution would be less likely than if Maras had signed
his own name.
  The defendants’ last line of defense is that the fraud was
harmless, as in cases of typographical errors and other
inadvertent technical irregularities, United States v. Skinner,

, 177 (7th Cir. 1992); United States v. Bentley, 

, 1109 (7th Cir. 1987); Hirschfeld v. United States, 

(7th Cir. 1931); United States v. 

; United
States v. Warren, 

, 653 (D.C. Cir. 1994), because
Maras, having been one of the arresting officers, was in as
good a position to sign the complaint in his own name as
Marozas was. But then it’s extremely odd that Maras didn’t
sign his own name. The defendants say it’s because Maras
wasn’t planning to be in court the day of the hearing, but it
seems that Marozas was planning to be there, so why didn’t
he sign his own name to the complaint? Well, maybe for
some undisclosed reason he wasn’t available to sign the
complaint, and in that event Maras could have signed for
him but should have indicated that that was what he was
doing, as by writing “per E.M.” under the purported sig-
nature of Marozas.
  Immaterial falsehoods, even deliberate ones, in an affi-
davit that is presented to a judge or magistrate in support of
a request for the issuance of an arrest or search warrant do
not invalidate the warrant should it be issued. Franks v.
Delaware, 

(1978); United States v. Jackson, 

, 573-75 (7th Cir. 1996); United States v. 

,
9 F.3d at 1342-44. The same is true regarding a sworn com-
10                                               No. 03-3175

plaint submitted to obtain a judicial finding of probable
cause to detain a person who has been arrested. See, besides
the cases cited earlier, Jones v. Cannon, 

, 1284-
85 (11th Cir. 1999). But this isn’t such a case. No one signs
another person’s name by accident; there is no indication
that Maras failed merely by inadvertence to indicate that he
was signing another person’s name; and a fraudulent
complaint cannot provide the sole basis for a finding of
probable cause. See United States v. Cortina, 

,
1213-17 (7th Cir. 1980); United States v. Hammond, 

, 773-74 (6th Cir. 2003). So although we agree with the
district court that the arrest itself was lawful, the grant of
summary judgment with respect to the continued detention
ordered by the judge at the Gerstein hearing was error, and
so the case must be remanded and the plaintiff’s sup-
plemental state-law claims, dismissed because the district
court dismissed the plaintiff’s federal claims before trial,
reinstated.
     AFFIRMED IN PART, REVERSED IN PART, AND REMANDED.

A true Copy:
        Teste:

                          _____________________________
                           Clerk of the United States Court of
                             Appeals for the Seventh Circuit




                    USCA-02-C-0072—8-10-04