                    FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

RAYMOND TORRES; MARIA ELVA               
ALMADOR-TORRES,
               Plaintiffs-Appellants,
                 v.                             No. 06-55817
CITY OF LOS ANGELES; LOS                          D.C. No.
ANGELES POLICE DEPARTMENT;                   CV-05-04171-RGK
BRAD ROBERTS, LAPD Detective;
                                                ORDER AND
JENNIFER HICKMAN, LAPD
                                                 OPINION
Detective; STEVE PARK, LAPD
Detective; F. RAINS, LAPD
Detective,
              Defendants-Appellees.
                                         
        Appeal from the United States District Court
           for the Central District of California
        R. Gary Klausner, District Judge, Presiding

                    Argued and Submitted
           February 12, 2008—Pasadena, California

               Opinion Filed August 26, 2008
           Opinion Withdrawn November 13, 2008

           New Opinion Filed November 13, 2008

       Before: Betty B. Fletcher and N. Randy Smith,
    Circuit Judges, and Samuel P. King,* District Judge.

                 Opinion by Judge B. Fletcher

   *The Honorable Samuel P. King, Senior United States District Judge
for the District of Hawaii, sitting by designation.

                               15339
                TORRES v. CITY OF LOS ANGELES            15343


                         COUNSEL

Nelson E. Brestoff (argued), Moskowitz, Brestoff, Winston &
Blinderman, LLP, Valencia, California, Julia A. Follansbee,
Follansbee & Associates, Bend, Oregon, for the plaintiffs-
appellants.

Rockard J. Delgadillo, Janet G. Bogigian, Amy Jo Field
(argued), Los Angeles City Attorney’s Office, Los Angeles,
California, for the defendants-appellees.


                          ORDER

  The Opinion filed August 26, 2008, slip op. 11723, and
appearing at ___ F.3d ___, 2008 WL 3905411 (9th Cir. Aug.
26, 2008), is withdrawn. It may not be cited as precedent by
or to this court or any district court of the Ninth Circuit.

  The panel has voted to deny the petition for panel rehear-
ing. Judge N.R. Smith votes to deny the petition for rehearing
en banc and Judges B. Fletcher and King so recommend.

  The full court has been advised of the petition for rehearing
en banc and no judge has requested a vote on whether to
rehear the matter en banc. Fed. R. App. P. 35.

  The petition for panel rehearing and the petition for rehear-
ing en banc are denied.

  The new Opinion is filed contemporaneously with this
order. There is no change in substance.
15344              TORRES v. CITY OF LOS ANGELES
  No new petition for rehearing or rehearing en banc will be
entertained.


                              OPINION

B. FLETCHER, Circuit Judge:

   In 2004, plaintiff Raymond Torres, who was then 16 years
old, was arrested, without a warrant, on charges of murder
and attempted murder. After 162 days of incarceration, Torres
was released when the district attorney dismissed the charges
against him. Following his release, Torres and his mother
(“Plaintiffs”) brought a civil rights action against the City of
Los Angeles, the Los Angeles Police Department (“LAPD”),
and four LAPD detectives (“Defendants”), seeking damages
under both federal and state law. After granting summary
judgment to the City of Los Angeles and the LAPD, the dis-
trict court denied two of Plaintiffs’ motions in limine and,
after all of the parties had presented their evidence to the jury,
granted the remaining Defendants’ motion for judgment as a
matter of law. Plaintiffs appeal the grant of the motion for
judgment as a matter of law as well as the rulings on the
motions in limine. We affirm in part, reverse in part, and
remand.

                                    I.

   The charges leading to Torres’ arrest arose from a gang-
related shooting in Los Angeles on August 11, 2004. On that
day, Josue Santillan, a member of the Canoga Park Alabama
street gang (“CPA gang”), was driving a car that contained
four other passengers: Diana H., who was seated in the front
right passenger seat; Joel Castaneda, who was seated in the
back seat directly behind Diana; and two other persons, at
least one of them male, who were also seated in the back seat.1
  1
   Diana, who was the detectives’ main source of information about the
shooting, gave different accounts of who was in the car other than herself,
                    TORRES v. CITY OF LOS ANGELES                     15345
At one point Santillan drove by a park in the Reseda area,
where, according to Diana and other witnesses, the male pas-
sengers flashed gang hand signs and shouted challenges at
members of the Reseda street gang who were in the park. San-
tillan then drove away, but the members of the Reseda gang
gave chase in a car of their own. When the Reseda gang mem-
bers’ car pulled alongside the car driven by Santillan, Cas-
taneda fired several rounds from a semiautomatic pistol at the
Reseda gang members’ car, killing the driver and wounding
another passenger.

   Detectives Roberts, Hickman, Park and Rains investigated
the shooting. On August 25, 2004, two weeks after the shoot-
ing, Detectives Roberts and Hickman questioned Diana about
the shooting. Diana identified Santillan as the driver and Cas-
taneda as the shooter, and both were subsequently arrested.
Diana also expressed her belief that all the male passengers
were probably members of the CPA gang.

   Detectives Roberts and Hickman asked Diana about the
third male passenger who had been sitting directly behind
Santillan. Diana told the detectives that she had never seen
him before, that she did not know his name, and that she did
not remember him well because she had not been paying
attention to him. However, Diana was able to describe this
third male passenger as Hispanic, 15 or 16 years old, with a
complexion darker than hers, and very overweight. Diana also
stated that he had some hair. She further described him as
having worn a white T-shirt, blue shorts, and white tennis
shoes. Detective Roberts acknowledged at trial that Diana’s
description was “too generic to go anywhere with it.”

Santillan and Castaneda. At first she stated that only one other person, a
male, was in the car; later she stated that two other persons were in the car,
one male and one female; and later still she stated that only two other
males were in the car.
15346              TORRES v. CITY OF LOS ANGELES
   On September 23, 2004, six weeks after the shooting, the
detectives obtained several additional pieces of information in
their investigation of the third male passenger, which led them
to arrest Torres that same day.

   First, Detective Hickman spoke to Danny Steinberg, a
school police officer assigned to El Camino High School. Pre-
viously, Steinberg had been questioned by an LAPD Juvenile
Officer, Marie Lamar, about an outstanding suspect in a mur-
der case. Officer Lamar had described the suspect as a short
and heavy-set Hispanic male with a shaved head who was
“dressed down gang-style.”2 Steinberg had informed Officer
Lamar that her description matched a student at El Camino—
Torres—and that Torres had recently begun hanging out with
gang members at El Camino and had begun “dressing down
as a gangster” and shaving his head. On September 23, Stein-
berg repeated the same information to Detective Hickman.
There was conflicting testimony at trial, however, as to
whether Steinberg also told Officer Lamar and Detective
Hickman that Torres had “recently been jumped into the CPA
gang,” i.e., that Torres had become a member of the gang.

   Second, Detectives Hickman and Roberts spoke to an offi-
cial at El Camino high school, Mark Pomerantz. Pomerantz
gave the detectives two color photos of Torres, one older, in
which Torres is shown with short dark hair, and the other
taken that morning at the detectives’ request, in which Torres
is shown with a shaven head. In addition, Pomerantz dis-
cussed with the detectives a group photo of six young His-
panic males—including Torres and Santillan—that Pomerantz
had provided the LAPD a year earlier when it was investigat-
ing Santillan in connection with another shooting of a Reseda
gang member. The group photo had been taken by a teacher
at a school event called “Melody of Words,” although Detec-
  2
    The record does not reveal how Officer Lamar had come to believe that
the third male passenger had a shaved head and was “dressed down gang-
style.”
                   TORRES v. CITY OF LOS ANGELES                     15347
tive Roberts testified at trial that he was unaware of that fact
at the time of Torres’ arrest.

   When Pomerantz originally provided the group photo he
had informed the LAPD that two of the individuals in the
photo (neither of them Torres) were members of the CPA
gang. On September 23, Pomerantz told the detectives that
Torres and Santillan were friends and hung out. In the group
photo, Torres’ right hand is not visible and only part of one
finger of his left hand is visible. Conflicting testimony was
presented at trial as to whether Torres is making a gang sign
with his left hand. However, Detectives Roberts and Park
both testified that, at the time of Torres’ arrest, they were
unaware one way or the other whether Torres was a member
of the CPA gang.

  In all three photos provided by Pomerantz, Torres is wear-
ing a prominent grey metal cross on a chain around his neck.
Pomerantz also told Detective Hickman that Torres “always
wears [a] grey metal cross on a chain around his neck.” Nota-
bly, Diana did not say anything about the third male passen-
ger in the car wearing a chain or cross when the detectives
spoke to her on August 25, 2004.

   Third, Detective Hickman searched Torres’ name in six dif-
ferent databases: an adult criminal records database, a juve-
nile records database, a Department of Motor Vehicles
records database, the California Criminal History Record Sys-
tem, the Cal-Gangs database, and the gang card file at the
West Valley police station. Detective Hickman found no
matches for Torres.

  Fourth, Detective Hickman used the most recent photo of
Torres she had received from Pomerantz to assemble a photo-
graphic identification array of six individuals called a “six-
pack.”3 Detective Hickman used a computer database to find
  3
   In the six-pack, the photo of Torres is cropped such that the cross hang-
ing from Torres’ neck chain is not visible.
15348           TORRES v. CITY OF LOS ANGELES
photos of five other individuals to place in the six-pack,
which she did by searching for photos based on age and phys-
ical characteristics also applicable to Torres. However, while
Detective Hickman first searched for photos of persons who
were not only young male Hispanics but also “heavy,” that
search did not yield a sufficiently large selection to fill the
six-pack with faces that Detective Hickman considered to be
similar to that of Torres. Accordingly, Detective Hickman
expanded her search to include non-heavy persons, which did
yield a sufficient large selection. Plaintiffs’ police procedures
expert testified at trial that the resulting six-pack was unduly
suggestive because aside from Torres’ photo only one other
photo was of a visibly “chubby” person, thus significantly
increasing the odds that Diana would “identify” Torres in the
lineup.

   Detectives Roberts, Park and Rains then proceeded to the
residence of Diana. Detectives Roberts and Park went inside
to show Diana the six-pack; Detective Rains waited outside in
his car. Detective Roberts told Diana that he “had possibly
identified the 15- to 16-year old chubby boy” and then read
her a standard “photographic show-up admonition.”

   After Detective Roberts handed Diana the six-pack, Diana
stared at it—according to Diana for between five and ten
minutes—whereupon Detective Roberts asked her at whom
she was staring. Diana then indicated that she was staring at
photo #6, the photo of Torres. However, there was conflicting
testimony as to whether Diana also stated that the person in
photo #6 was the third male passenger in the car, or, on the
contrary, whether she stated that she did not know whether it
was him or not. It is undisputed, however, that the detectives
then asked Diana to write down what she thought, whereupon
Diana circled the photo of Torres with a pen and wrote on the
six-pack, “I circle the person in #6 because he looks more
likely [sic] to the other guy in the car.” Detective Roberts
acknowledged at trial that, based solely on what Diana wrote
                TORRES v. CITY OF LOS ANGELES              15349
on the six-pack, he did not have probable cause to arrest Tor-
res.

   When Detectives Roberts and Park rejoined Detective
Rains outside Diana’s home, Detective Roberts told Rains
that Diana had identified Torres as the third male passenger—
a statement which Diana testified at trial was false—and said
they were going to arrest Torres. Detective Rains was not
shown Diana’s written statement on the six-pack. Detectives
Roberts, Park and Rains then went to Torres’ home. When
Torres came outside and the detectives approached him, Tor-
res did not try to flee. The detectives engaged in no conversa-
tion with Torres but simply arrested him in his mother’s
presence. Detective Park acknowledged at trial that at the time
of Torres’ arrest there was no physical evidence linking Tor-
res to the shooting.

  Torres was charged with murder and attempted murder
based on his alleged role in the shooting of the two Reseda
gang members. However, on March 4, 2005, after 162 days
of incarceration, Torres was released when the district attor-
ney dismissed the charges against him.

   Torres and his mother subsequently filed suit, claiming
deprivation of Torres’ Fourth Amendment rights, in violation
of 42 U.S.C. § 1983, as well as false arrest and negligent
infliction of emotional distress, in violation of California law.
Defendants moved for partial summary judgment on Plain-
tiffs’ claims against the City of Los Angeles and the LAPD
on the ground that Plaintiffs could not prove liability under
Monell v. New York City Department of Social Services, 436
U.S. 658 (1978). In their motion, Defendants stated that
“[b]ecause triable issues of material fact exist regarding prob-
able cause for Plaintiff’s arrest, Defendants move for partial
summary judgment on Monell liability only.” The district
court granted the motion, a ruling Plaintiffs do not appeal.

   On the eve of trial against the remaining Defendants, the
district court denied two of Plaintiffs’ motions in limine: a
15350               TORRES v. CITY OF LOS ANGELES
motion for an order barring Defendants’ expert witnesses
Detective Jack Giroud and Officer Norm Peters from testify-
ing on the ground that they had failed to provide written
expert reports as required by Federal Rule of Civil Procedure
26(a)(2)(B); and a motion for an order barring the investigat-
ing detectives and all defense experts from testifying that, in
their opinion, probable cause existed to arrest Torres.

   After all of the parties had presented their evidence to the
jury, Defendants orally moved for judgment as a matter of
law, pursuant to Federal Rule of Civil Procedure 50(a), as to
all of Plaintiffs’ claims. The district court granted the motion
and dismissed Plaintiffs’ case. In its written order, the district
court concluded that Detectives Hickman and Rains had not
been involved in Torres’ arrest and therefore could not be lia-
ble. The court further concluded that Detectives Park and
Roberts had probable cause to arrest Torres and that, accord-
ingly, Plaintiffs’ § 1983 claim and state law claims should be
dismissed.4 Finally, the court concluded that even if Detec-
tives Park and Roberts did not have probable cause to arrest
Torres, they were protected from Plaintiffs’ § 1983 claim by
qualified immunity.5

                                     II.

   We review de novo the district court’s order granting
  4
     The district court dismissed Plaintiffs’ state law claim for negligent
infliction of emotional distress because it was predicated on their claims
for violation of civil rights and false arrest.
   5
     In its written order, the district court made findings of fact and reached
conclusions of law as “required by Rule 52 of the Federal Rules of Civil
Procedure.” This was error because the case was being tried to a jury. See
Fed. R. Civ. P. 52(a)(1) (“In an action tried on the facts without a jury or
with an advisory jury, the court must find the facts specially and state its
conclusions of law separately.” (emphasis added)). Instead, the court
should have determined only whether “a reasonable jury would not have
a legally sufficient evidentiary basis” to find for the non-moving party. See
Fed. R. Civ. P. 50(a)(1).
                TORRES v. CITY OF LOS ANGELES            15351
Defendants’ motion for judgment as a matter of law under
Rule 50(a). See Santos v. Gates, 287 F.3d 846, 851 (9th Cir.
2002). “Judgment as a matter of law is appropriate when the
evidence presented at trial permits only one reasonable con-
clusion.” Id. In other words, “[a] motion for a judgment as a
matter of law is properly granted only if no reasonable juror
could find in the non-moving party’s favor.” El-Hakem v. BJY
Inc., 415 F.3d 1068, 1072 (9th Cir. 2005). “The evidence
must be viewed in the light most favorable to the nonmoving
party, and all reasonable inferences must be drawn in favor of
that party.” LaLonde v. County of Riverside, 204 F.3d 947,
959 (9th Cir. 2000). “If conflicting inferences may be drawn
from the facts, the case must go to the jury.” Id.

   We also review de novo the district court’s finding of prob-
able cause, Rosenbaum v. City and County of San Francisco,
484 F.3d 1142, 1161 n.14 (9th Cir. 2007), as well as its grant
of qualified immunity, Aguilera v. Baca, 510 F.3d 1161, 1167
(9th Cir. 2007). We review for an abuse of discretion the dis-
trict court’s evidentiary rulings. Janes v. Wal-Mart Stores,
Inc., 279 F.3d 883, 886 (9th Cir. 2002).

                             III.

                              A.

   [1] We affirm the district court’s dismissal of Plaintiffs’
case against Detective Hickman. The evidence is undisputed
that Detective Hickman was not present when Torres was
arrested, and there is no evidence that Detective Hickman
instructed the other detectives to arrest Torres or that any of
those detectives consulted with her before making the arrest.
Thus, there is no evidence of “integral participation” by
Detective Hickman in the alleged constitutional violation.
Chuman v. Wright, 76 F.3d 292, 294-95 (9th Cir. 1996); see
Blankenhorn v. City of Orange, 485 F.3d 463, 481 n.12 (9th
Cir. 2007) (explaining that integral participation requires
“some fundamental involvement in the conduct that allegedly
15352               TORRES v. CITY OF LOS ANGELES
caused the violation” and affirming summary judgment in
favor of officer who arrived on the scene after the allegedly
unconstitutional arrest and officer who provided only crowd
control (citing Boyd v. Benton County, 374 F.3d 773, 780 (9th
Cir. 2004)); Motley v. Parks, 432 F.3d 1072, 1082 (9th Cir.
2005) (en banc) (affirming grant of summary judgment in
favor of government agent who did not participate in the
allegedly unconstitutional search).

   [2] Moreover, although Detective Park testified that Detec-
tive Hickman, together with Detective Roberts, was in charge
of the investigation of the shooting, there is no evidence that
Detective Hickman acted as a supervisor that would impose
supervisor liability. See Motley, 432 F.3d at 1081 (“A supervi-
sor can be liable under § 1983 if he ‘set[s] in motion a series
of acts by others . . . , which he knew or reasonably should
have known, would cause others to inflict the constitutional
injury.’ ” (modifications in original) (quoting Larez v. City of
Los Angeles, 946 F.2d 630, 646 (9th Cir. 1991)).

                                      B.

  Plaintiffs argue that the district court erred in concluding,
as a matter of law, that Detectives Roberts, Park and Rains
had probable cause to arrest Torres.6

   [3] “Probable cause to arrest exists when officers have
knowledge or reasonably trustworthy information sufficient to
lead a person of reasonable caution to believe that an offense
has been or is being committed by the person being arrested.”
United States v. Lopez, 482 F.3d 1067, 1072 (9th Cir. 2007)
  6
    While the district court dismissed Plaintiffs’ case against Detective
Rains on the ground that “there was no evidence showing that Rains was
involved in the arrest of Plaintiff” because “[a]ccording to the evidence,
Rains was only acting as backup during Plaintiff’s arrest and did not per-
sonally assist in or direct the arrest of Plaintiff,” we disagree with this con-
clusion in light of Rains’ own testimony that “I was involved in the
arrest.”
                    TORRES v. CITY OF LOS ANGELES                    15353
(citing Beck v. Ohio, 379 U.S. 89, 91 (1964)). “While conclu-
sive evidence of guilt is of course not necessary under this
standard to establish probable cause, ‘[m]ere suspicion, com-
mon rumor, or even strong reason to suspect are not
enough.’ ” Id. (quoting McKenzie v. Lamb, 738 F.2d 1005,
1008 (9th Cir. 1984)). Under the collective knowledge doc-
trine, in determining whether probable cause exists for arrest,
we look to “the collective knowledge of all the officers
involved in the criminal investigation[.]” United States v.
Ramirez, 473 F.3d 1026, 1032 (9th Cir. 2007) (internal quota-
tion marks omitted).

   [4] As the definition of probable cause indicates, the proper
inquiry is whether the detectives had probable cause to
believe that Torres had committed a crime, not merely that
Torres was the third male passenger in the car.7 While proba-
ble cause supports an arrest so long as the arresting officers
had probable cause to arrest the suspect for any criminal
offense, regardless of their stated reason for the arrest, see
Devenpeck v. Alford, 543 U.S. 146, 153-55 (2004); see also
Virginia v. Moore, 128 S. Ct. 1598, 1604 (2008), an arrest is
still unlawful unless probable cause existed under a specific
criminal statute, see Devenpeck, 543 U.S. at 156. Defendants
do not contend that there was probable cause to believe that
Torres had committed any offense besides murder and
   7
     Defendants assert that Plaintiffs’ case “has always rested on whether
there was probable cause to believe that [Torres] was the third suspect in
[Diana’s] vehicle,” not on whether there was probable cause to believe
that Torres was guilty of murder. However, we consider only the latter
question because an arrest is lawful under the Fourth Amendment only if
it is accompanied by probable cause to believe that the arrestee has com-
mitted, or is committing, an offense. See, e.g., Lopez, 482 F.3d at 1072.
Mere presence in a vehicle in which a crime is being committed is not an
offense. See United States v. Herrera-Gonzalez, 263 F.3d 1092, 1097-98
(9th Cir. 2001) (“Sometimes youthful inexperience and lack of common
sense, impecuniousness, or personal relationships may bring the innocent
into continuing proximity with the guilty, but our line of ‘mere presence’
cases requires acquittal in the absence of evidence of intentional participa-
tion.”).
15354               TORRES v. CITY OF LOS ANGELES
attempted murder. In California, both offenses require an
unlawful killing with malice aforethought, see Cal. Penal
Code §§ 187, 664, although malice is implied “when a killing
results from an intentional act, the natural consequences of
which are dangerous to human life, and the act is deliberately
performed with knowledge of the danger to, and with con-
scious disregard for, human life[,]” People v. Cook, 139 P.3d
492, 515 (Cal. 2006) (citation omitted). Therefore, the ques-
tion is whether the detectives had probable cause to believe
that Torres had acted in concert with the shooter, Castaneda,
with conscious disregard for human life.8

   In reviewing the grant of a motion for judgment as a matter
of law, we must determine whether a reasonable jury could
have concluded that the detectives lacked probable cause to
arrest Torres. See, e.g., Monroe v. City of Phoenix, Arizona,
248 F.3d 851, 861-62 (9th Cir. 2001) (affirming denial of
Rule 50(a) motion in excessive force case because “[a] rea-
sonable jury could conclude that [the defendant officer] had
probable cause to believe that [the plaintiff] posed a threat of
serious physical harm”), overruled on other grounds as rec-
ognized in Acosta v. Hill, 504 F.3d 1323, 1324 (9th Cir.
  8
    Defendants “presume” that Torres was arrested and charged with mur-
der on a provocative act murder theory, a theory that can be applied in
“situations in which criminal defendants neither kill nor intend to kill, but
cause a third party to kill in response to their life-threatening provocative
acts.” People v. Cervantes, 29 P.3d 225, 230 (Cal. 2001). However, to the
extent Defendants suggest that Torres’ alleged flashing of gang signs and
shouting of challenges, alone, could constitute the intentional act neces-
sary for murder liability, we disagree. “To satisfy the ‘actus reus’ element
of [provocative act murder] the defendant or one of his confederates must
commit an act which provokes a third party into firing the fatal shot.” In
re Aurelio R., 212 Cal. Rptr. 868, 870 (Cal. Ct. App. 1985). “[N]o criminal
liability attaches to an initial remote actor for an unlawful killing that
results from an independent intervening cause (i.e., a superseding cause).”
Cervantes, 29 P.3d at 231. Here, the evidence shows that Castaneda fired
the shots not because he was provoked by his fellow passenger’s flashing
of gang signs and shouting of challenges, but rather by the fact that the
Reseda gang members chased the car driven by Santillan.
                TORRES v. CITY OF LOS ANGELES             15355
2007). Defendants concede that, because we must view the
evidence in the light most favorable to Plaintiffs and draw all
reasonable inferences in their favor, we must assume the fol-
lowing: that school police officer Steinberg did not tell Offi-
cer Lamar or Detective Hickman that Torres had “recently
been jumped into the CPA gang”; that in the group photo Tor-
res is not visibly making a gang sign (or that it was unreason-
able for the detectives to conclude that he is); and that Diana
did not positively identify Torres as the third male passenger
in the car.

   We conclude that, based on the information in the detec-
tives’ possession at the time of the arrest, a reasonable jury
could have found that the detectives lacked probable cause to
believe that Torres had been the third male passenger in the
car and had acted in concert with the shooter with conscious
disregard for human life.

   [5] First, Diana’s general description of the third male pas-
senger is not sufficient to create probable cause. “ ‘Under the
law of this Circuit, mere resemblance to a general description
is not enough to establish probable cause.’ ” Lopez, 482 F.3d
at 1073 (quoting Grant v. City of Long Beach, 315 F.3d 1081,
1088 (9th Cir. 2002), amended by 334 F.3d 795 (9th Cir.
2002). For example, in United States v. Ricardo D., we held
that the fact that the defendant matched descriptions of the
crime suspect as a “young, thin man, not too tall” and a
“young, Mexican male” were insufficient to create probable
cause. 912 F.2d 337, 342 (9th Cir. 1990). Here, Diana’s
description of the third male passenger was slightly more
detailed than the description in Ricardo D. but, at the same
time, did not match Torres insofar as Diana described the
third male passenger as having some hair. Moreover, the fact
that Diana did not mention a chain or cross around the passen-
ger’s neck casts further doubt on whether Torres matched
Diana’s general description. Accordingly, Diana’s description
alone was clearly insufficient to create probable cause as a
matter of law.
15356            TORRES v. CITY OF LOS ANGELES
   [6] Second, a reasonable jury could have found that Diana’s
“identification” of Torres in the six-pack did not create proba-
ble cause because the six-pack was suggestive and the “identi-
fication” was not sufficiently reliable. See Grant, 315 F.3d at
1086-88 (holding that two identifications did not create proba-
ble cause as a matter of law because six-pack was arguably
suggestive and identifications lacked sufficient indicia of reli-
ability).

   The Supreme Court has cautioned that “[a] major factor
contributing to the high incidence of miscarriage of justice
from mistaken identification has been the degree of sugges-
tion inherent in the manner in which the prosecution presents
the suspect to witnesses for pretrial identification.” United
States v. Wade, 388 U.S. 218, 228 (1967). Here, only one
other photo in the six-pack besides the photo of Torres was
of a visibly overweight individual and thus of a person who
fit Diana’s general description. In addition, Detective Roberts
told Diana, before handing her the six-pack, that the detec-
tives had “possibly identified the 15 to 16 year-old chubby
boy.” According to Plaintiffs’ expert, that statement was “ab-
solutely forbidden” and “contamine[d] the identification,”
presumably because it informed Diana that the detectives’
suspect was among the photos in the six-pack and thus could
have pressured her to make an identification. Based on these
facts, a reasonable jury could have found the six-pack to be
impermissibly suggestive.

   Although a suggestive photo array “may still serve as a
basis for probable cause if sufficient indicia of reliability are
present,” Grant, 315 F.3d at 1087 (citing United States v.
Hanigan, 681 F.2d 1127, 1131 (9th Cir. 1982)), here a reason-
able jury could have found that no sufficient indicia of reli-
ability were present. “Indicia of reliability include: 1) the
opportunity to view the criminal at the time of the crime; 2)
the degree of attention paid to the criminal; 3) the accuracy
of the prior descriptions of the criminal; 4) the level of cer-
tainty demonstrated at the time of the confrontation; and 5) [ ]
                TORRES v. CITY OF LOS ANGELES              15357
the length of time between the crime and the confrontation.”
Id. (citing Gray v. Klauser, 282 F.3d 633, 639 (9th Cir.
2002)). While Diana spent several hours in the car with the
third male passenger, she had never seen him before and did
not pay attention to him. In addition, as previously discussed,
Diana gave only a general description of the third male pas-
senger, which did not match Torres in two important respects
(head of hair and no mention of prominent cross). Further,
Diana was not shown the six-pack until six weeks after the
shooting. When she was handed the six-pack, she stared at it
in silence for between five and ten minutes and then, when
asked at whom she was staring, made only a comparative
identification: she stated that Torres looked more like the
third male passenger than the other persons depicted in the
six-pack (only one of whom was visibly overweight), but that
she was not sure whether or not it actually was him. Thus, a
reasonable jury could have concluded that Diana’s identifica-
tion lacked sufficient indicia of reliability and thus did not
provide the detectives with probable cause. Although Detec-
tive Rains had been told that Diana had positively identified
Torres, we nevertheless conclude that the reliability of the
identification was sufficiently questionable for other reasons
to allow a reasonable jury to conclude that Rains, too, lacked
probable cause.

   [7] While the detectives also had the additional information
that Torres was friends with Santillan, hung out with gang
members, and had recently begun “dressing down as a gang-
ster,” they had no information that Torres was actually a
member of the CPA gang (or any other gang), and Torres’
name did not come up in any of the six criminal databases
searched by Detective Hickman. Moreover, although finger-
prints of Santillan were found in the car, there was no physi-
cal evidence linking Torres to the vehicle. In addition, the fact
that Torres made no attempt to flee when the detectives came
to arrest him, while by no means dispositive, further indicates
that reasonable minds could disagree about the existence of
probable cause. See Ricardo D., 912 F.2d at 342.
15358           TORRES v. CITY OF LOS ANGELES
   [8] Finally, the detectives lacked evidence that the third
male passenger had acted in concert with Castaneda and had
the requisite mental state to be guilty of murder and attempted
murder. There is no evidence that the third male passenger
helped decide or make plans to challenge or shoot at rival
gang members; that he knew that Castaneda had a gun; or that
he assisted Castaneda in firing the shots. Thus, aside from the
evidence that the third male passenger had flashed gang signs
and shouted challenges, there was no evidence that the third
male passenger had acted in concert with Castaneda and had
done so with a conscious disregard for human life. This dearth
of evidence as to the third male passenger’s culpability further
widens the gap between mere suspicion and probable cause to
believe that Torres had committed a crime.

  [9] Accordingly, we conclude that a reasonable jury could
have found that Detectives Roberts, Park and Rains lacked
probable cause to believe that Torres had committed a crime.
The district court therefore erred in finding probable cause as
a matter of law.

                              C.

   We next consider whether Detectives Roberts, Park and
Rains were nevertheless protected by qualified immunity.
When a police officer asserts qualified immunity, we apply a
two-part analysis under Saucier v. Katz, 533 U.S. 194 (2001).
The first question is whether the facts, when taken in the light
most favorable to Plaintiffs, show that Defendants’ conduct
violated a constitutional right. Id. at 201. The second question
is whether the constitutional right at issue is “clearly estab-
lished.” Id. at 202.

   As Defendants argue, qualified immunity is a question of
law, not a question of fact. Hunter v. Bryant, 502 U.S. 224
(1991). But Defendants are only entitled to qualified immu-
nity as a matter of law if, taking the facts in the light most
favorable to Torres, they violated no clearly established con-
                 TORRES v. CITY OF LOS ANGELES               15359
stitutional right. The court must deny the motion for judgment
as a matter of law if reasonable jurors could believe that
Defendants violated Torres’ constitutional right, and the right
at issue was clearly established.

   [10] Plaintiffs here appeal the grant of a Rule 50(a) motion
made after completion of the trial but before a jury verdict.
While the Supreme Court has encouraged resolution of the
qualified immunity issue early on in the lawsuit, such as at the
summary judgment stage, see Saucier, 533 U.S. at 200
(“Where the defendant seeks qualified immunity, a ruling on
that issue should be made early in the proceedings so that the
costs and expenses of trial are avoided where the defense is
dispositive.”), Defendants chose not to move for summary
judgment on qualified immunity grounds, acknowledging that
“triable issues of material fact exist regarding probable cause
for Plaintiff’s arrest.” Thus, the case proceeded to trial before
a jury. However, the same issues of material fact also prevent
the court from granting the officers’ motion for judgment as
a matter of law. See, e.g., Grant, 315 F.3d at 1090 (denying
officers’ motion for judgment as a matter of law on qualified
immunity because “viewed in the light most favorable to the
non-moving party, there was enough evidence for a reason-
able jury to conclude that reasonable officers would not have
acted as [the defendants] did in arresting [the plaintiff].”);
LaLonde, 204 F.3d at 953 (“If . . . there is a material dispute
as to the facts regarding what the officer or the plaintiff actu-
ally did, the case must proceed to trial, before a jury if
requested.” (citing Act Up!/Portland v. Bagley, 988 F.2d 868,
873 (9th Cir. 1993)); Thompson v. Mahre, 110 F.3d 716, 719
(9th Cir. 1997) (“[W]here there is a genuine issue of fact on
a substantive issue of qualified immunity, ordinarily the con-
trolling principles of summary judgment and, if there is a jury
demand and a material issue of fact, the Seventh Amendment,
require submission to a jury.”); see also Sloman v. Tadlock,
21 F.3d 1462, 1468 (9th Cir. 1994) (explaining that the rea-
sons for the existence of the qualified immunity doctrine “do
not . . . suggest that a judicial determination at [the trial] stage
15360              TORRES v. CITY OF LOS ANGELES
is necessarily better than a jury verdict” (emphasis in original)).9
Indeed, we have explained that “sending the factual issues to
the jury but reserving to the judge the ultimate ‘reasonable
officer’ determination leads to serious logistical difficulties.”
Sloman, 21 F.3d at 1468.

   [11] Defendants contend that our decision in Peng v. Mei
Chin Penghu, 335 F.3d 970 (9th Cir. 2003), supports their
contention that a court, not a jury, must decide the qualified
immunity issue here. We disagree. In Peng, the district court
had determined at the summary judgment stage that the defen-
dant officer was entitled to qualified immunity. Id. at 972-73.
On appeal, Peng argued, first, that the existence of disputes of
fact precluded the district court from granting summary judg-
ment on the issue of qualified immunity, and, second, that
because more than one reasonable inference could be drawn
from the undisputed facts regarding the existence of probable
cause, the question of probable cause was one for the jury and
not the court. Id. at 978-79. Rejecting both arguments, this
court held that the factual disputes were not material to the
qualified immunity issue, id., and that, “where the material,
historical facts are not in dispute, and the only disputes
involve what inferences properly may be drawn from those
historical facts, it is appropriate for this court to decide
whether probable cause existed at the time [the officer]
arrested Peng,” id. at 979-80 (emphasis added).

   [12] However, in this case historical facts material to the
qualified immunity determination are in dispute. Disputes of
fact exist as to whether Diana positively identified Torres,
whether school police officer Steinberg told Officer Lamar
and/or Detective Hickman that Torres had “recently been
jumped into the CPA gang,” and whether it was reasonable
  9
    As we noted in Sloman, when a case proceeds to trial “qualified immu-
nity can no longer rightly be called an ‘immunity from suit’ (since the suit
has already proceeded to its conclusion); rather, it is now effectively a
defense.” 21 F.3d at 1468 n.6.
                 TORRES v. CITY OF LOS ANGELES             15361
for the detectives to believe that in the group photo Torres
was making a gang sign despite the fact that only one of Tor-
res’ fingers is visible in the photo. These disputes of fact are
material because they go to what the detectives knew at the
time they arrested Torres and, accordingly, to whether they
had probable cause, and reasonably believed they had proba-
ble cause, to do so. Taking these facts in the light most favor-
able to Torres, a reasonable officer would have known that he
lacked probable cause for the arrest. Accordingly, Peng does
not help Defendants.

   With respect to the first Saucier question, we have already
determined that a reasonable jury could find that Defendants
violated Torres’ constitutional right to be free from arrest
without probable cause. See Grant, 315 F.3d at 1089 (“Courts
have long held that the Fourth Amendment requires probable
cause before an officer may arrest an individual.” (citing
Beck, 379 U.S. at 91)). In answering the second question,
whether the constitutional right was clearly established, we do
not consider the right as a “general proposition.” Saucier, 533
U.S. at 201. Rather, “[t]he relevant, dispositive inquiry . . . is
whether it would be clear to a reasonable officer that his con-
duct was unlawful in the situation he confronted.” Id. at 202.
“Qualified immunity is an objective inquiry—whether the
officers subjectively believed that they had probable cause to
arrest [Torres] is irrelevant.” Grant, 315 F.3d at 1089 (citing
Anderson v. Creighton, 483 U.S. 635, 641 (1987)).

   [13] In light of the arguably suggestive six-pack, Diana’s
merely comparative identification six weeks after the shoot-
ing, the lack of direct evidence that Torres was a member of
a gang (let alone the CPA gang), the lack of physical evidence
tying Torres to the shooting, the fact that Torres did not
attempt to flee when the detectives approached him, and the
lack of evidence that the third male passenger acted in concert
with Castaneda with conscious disregard for human life, “[a]
material issue of fact existed as to whether a reasonable offi-
cer would have relied on [the information in the detectives’
15362           TORRES v. CITY OF LOS ANGELES
possession] without further verification.” Grant, 315 F.3d at
1090. Accordingly, “there was enough evidence for a reason-
able jury to conclude that reasonable officers would not have
acted as [Detectives Roberts and Park] did in arresting [Tor-
res].” Id. We therefore conclude that Detectives Roberts and
Park were not entitled to qualified immunity as a matter of
law.

   However, we reach a different conclusion as to Detective
Rains. Because Detective Roberts told Rains that Diana had
identified Torres and because he did not show Rains Diana’s
written statement on the six-pack, Rains believed that Diana
had positively identified Torres.

   While “[a]ll officers . . . have an ongoing duty to make
appropriate inquiries regarding the facts received or to further
investigate if sufficient details are relayed,” Motley, 432 F.3d
at 1081 (citation omitted), we have explained that “[w]here an
officer has an objectively reasonable, good-faith belief that he
is acting pursuant to proper authority, he cannot be held liable
if the information supplied by other officers turns out to be
erroneous.” id. at 1082 (citing United States v. Hensley, 469
U.S. 221, 232 (1985)). “The lynchpin is whether the officer’s
reliance on the information was objectively reasonable.” Id.

   [14] In light of what Detective Roberts told Detective Rains
after showing the six-pack to Diana, and in light of the undis-
puted fact that, of the four detectives, Detective Rains was the
least involved in the investigation, we conclude as a matter of
law that Detectives Rains reasonably relied on the (allegedly
false) statement by Detective Roberts that Diana had identi-
fied Torres. Based on this conclusion, we further conclude as
a matter of law that a reasonable officer in Rains’ position
would have believed he had probable cause to arrest Torres.
Accordingly, Detective Rains was entitled to qualified immu-
nity as a matter of law.
                       TORRES v. CITY OF LOS ANGELES                      15363
                                        D.

   We deal with the following evidentiary issues to guide the
district court on remand. Plaintiffs contend that the district
court abused its discretion in denying their motion in limine
seeking to bar the testimony of Defendants’ expert witnesses
Detective Jack Giroud and Officer Norm Peters on the ground
that Defendants failed to provide Plaintiffs written expert
reports for those witness pursuant to Federal Rule of Civil
Procedure 26(a)(2)(B).

   Rule 26(a)(2)(B) provides that, “[u]nless stipulated or
ordered by the court, [the disclosure of the identity of wit-
nesses pursuant to Rule 26(a)(2)(A)] must be accompanied by
a written report—prepared and signed by the witness—if the
witness is one retained or specially employed to provide
expert testimony in the case or one whose duties as the party’s
employee regularly involve giving expert testimony.” Fed. R.
Civ. P. 26(a)(2)(B). We have explained that “Rule 37(c)(1)
gives teeth to [this requirement] by forbidding the use at trial
of any information required to be disclosed by Rule 26(a) that
is not properly disclosed.” Yeti by Molly, Ltd. v. Deckers Out-
door Corp., 259 F.3d 1101, 1106 (9th Cir. 2001).10

   [15] We agree with Plaintiffs that Officer Peters should not
have been permitted to testify without providing a written
expert report. Peters, whom Defendants called as a “gang spe-
cialist,” testified that he was regularly employed to give
expert opinions in court about gangs. Accordingly, Peters falls
  10
    Rule 37(c)(1) provides in relevant part:
       If a party fails to provide information or identify a witness as
       required by Rule 26(a) or (e), the party is not allowed to use that
       information or witness to supply evidence on a motion, at a hear-
       ing, or at trial, unless the failure was substantially justified or is
       harmless.
Fed. R. Civ. P. 37(c)(1).
15364            TORRES v. CITY OF LOS ANGELES
squarely in the category of witnesses to which Rule
26(a)(2)(B) applies.

   We reject Defendants’ argument that Plaintiffs were
required, but failed, to articulate how they would be preju-
diced if they were not provided an expert witness report.
Defendants advance two bases for their argument. First, they
contend that the purpose of an expert report is “the elimina-
tion of unfair surprise to the opposing party and the conserva-
tion of resources,” Sylla-Sawdon v. Uniroyal Goodrich Tire
Co., 47 F.3d 277, 284 (8th Cir. 1995), and that because “Rule
26 focuses not on the status of the witness, but rather on the
substance of the testimony,” Patel v. Gayes, 984 F.2d 214,
218 (7th Cir. 1993) (superseded on other grounds by amend-
ment to the Federal Rules of Civil Procedure, as recognized
in Musser v. Gentiva Health Servs., 356 F.3d 751, 757 n.2
(7th Cir. 2004)), Plaintiffs must articulate how the failure to
provide them with an expert report led to surprise at trial. This
contention fails. In Patel, the Seventh Circuit focused on the
substance of the testimony rather than the status of the witness
not to determine whether the party moving under Rule 26
would be prejudiced by the lack of an expert report but only
to determine whether the witnesses in question were experts
for purposes of Rule 26(a)(2)(B) or instead fell under the
“treating physician” exception and therefore were not
required to prepare an expert report in the first place. See
Patel, 984 F.2d at 218. Thus, Patel does not support Defen-
dants’ argument.

   The second basis for Defendants’ argument is that Rule
37(c)(1) provides that a party who fails to comply with Rule
26(a) may not use the witness in question to supply evidence
at trial “unless the failure was substantially justified or is
harmless.” Fed. R. Civ. P. 37(c)(1) (emphasis added). Based
on this Rule, Defendants contend that Officer Peters could
testify without providing an expert report because Plaintiffs
failed to articulate how they would be prejudiced without
such a report. This contention also fails. Rule 37(c)(1) pro-
                TORRES v. CITY OF LOS ANGELES             15365
vides a sanction for failure to comply with the disclosure
requirements of Rule 26(a). See Fed R. Civ. P. 37 advisory
committee’s note, 1993 Amendments. In determining whether
this sanction should be imposed, the burden is on the party
facing the sanction—i.e., Defendants—to demonstrate that the
failure to comply with Rule 26(a) is substantially justified or
harmless. See Yeti by Molly, Ltd., 259 F.3d at 1107 (“Implicit
in Rule 37(c)(1) is that the burden is on the party facing sanc-
tions to prove harmlessness.”). Thus, Plaintiffs were not
required to articulate how they would be prejudiced by Defen-
dants’ failure to provide an expert report. Because the district
court denied Plaintiffs’ motion in limine without explanation,
there is no basis for us to conclude that the failure to provide
an expert report was substantially justified or harmless for
purposes of Rule 37(c)(1).

   [16] Therefore, we conclude that the district court abused
its discretion in denying Plaintiffs’ in limine motion. We
instruct the court, on remand and upon proper motion by
Plaintiffs, to require that Defendants, pursuant to Rule
26(a)(2)(B), provide Plaintiffs with an expert report prepared
by Officer Peters if they wish to call him as an expert witness.

   However, we do not reach the same conclusion with respect
to Detective Giroud. While Defendants concede that Detec-
tive Giroud was an expert witness, not all expert witnesses
must provide an expert report. By exclusion, Rule 26(a)(2)(B)
contemplates that individuals who are employed by a party
and whose duties do not regularly involve giving expert testi-
mony need not provide an expert report. See, e.g., Watson v.
United States, 485 F.3d 1100, 1107 (10th Cir. 2007); Bank of
China, New York Branch v. NBM LLC, 359 F.3d 171, 182
n.13 (2d Cir. 2004). We have found no evidence in the record
that the duties of Detective Giroud, who was employed by the
LAPD, regularly involved giving expert testimony. Accord-
ingly, on this record, we cannot determine whether Rule
26(a)(2)(B) applied to him. We therefore leave it to the dis-
trict court, on remand, to determine whether Rule 26(a)(2)(B)
15366               TORRES v. CITY OF LOS ANGELES
requires Defendants to provide Plaintiffs with an expert report
prepared by Detective Giroud.11

                                    IV.

  We affirm the district court’s dismissal of Plaintiffs’ case
against Detective Hickman and of Plaintiffs § 1983 claim
against Detective Rains.12 We reverse the grant of judgment
as a matter of law as to Detectives Roberts and Park. We
reverse in part the denial of Plaintiffs’ in limine motions.

   [17] Plaintiffs are awarded costs on appeal.

 AFFIRMED in part, REVERSED in part, and
REMANDED.




  11
      Keeping in mind that the inquiry is whether objectively the officers
reasonably believed they had probable cause, we also agree with Plaintiffs
that the district court abused its discretion in denying their motion in
limine seeking to bar Defendants’ witnesses from testifying as to their
own opinion about whether there was probable cause to arrest Torres. See
Stuart v. United States, 23 F.3d 1483, 1487 (9th Cir. 1994) (upholding dis-
trict court’s ruling that barred plaintiff’s expert from opining as to whether
probable cause existed on the ground that the jury was more suited than
the expert to answer the question); see also Peterson v. City of Plymouth,
60 F.3d 469, 476 n.10 (8th Cir. 1995); Estes v. Moore, 993 F.2d 161, 163
(8th Cir. 1998). Defendants did not address this issue in their brief and
effectively conceded the issue at oral argument. Accordingly, we instruct
the district court, on remand, to bar Defendants’ witnesses from testifying
as to their opinion that they had probable cause to arrest Torres.
   12
      Because we conclude that a reasonable jury could have found that all
Defendants, including Detective Rains, lacked probable cause to arrest
Torres, Plaintiffs’ California law claims against Detective Rains, which
are not affected by our conclusion that Rains is protected by qualified
immunity, should not have been dismissed. See Blankenhorn, 485 F.3d at
489 (Berzon, J., concurring in part and dissenting in part); Brown v. Li,
308 F.3d 939, 955 (9th Cir. 2002).
