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

No. 06-2192
UNITED STATES OF AMERICA,
                                               Plaintiff-Appellee,
                                v.

WILLIE P. DABNEY,
                                           Defendant-Appellant.
                         ____________
           Appeal from the United States District Court
      for the Northern District of Illinois, Eastern Division.
            No. 05 CR 576—John W. Darrah, Judge.
                         ____________
   ARGUED JANUARY 10, 2007—DECIDED AUGUST 2, 2007
                   ____________


 Before POSNER, MANION, and SYKES, Circuit Judges.
  SYKES, Circuit Judge. Willie Dabney was convicted of
being a felon in possession of a firearm in violation of 18
U.S.C. § 922(g)(1) and sentenced to the statutory maxi-
mum of 120 months. Dabney challenges the introduc-
tion at trial of evidence regarding his prior admission in
state court to possessing the firearm in question. He
further maintains that both the district court and the
government violated his rights under Brady v. Maryland,

(1963), that there was insufficient evidence to
support his conviction, and that his sentence failed to
adequately reflect the factors set forth in 18 U.S.C.
§ 3553(a)(2). We affirm his conviction and his sentence.
2                                             No. 06-2192

                    I. Background
  Late on the night of December 31, 2004, and into the
early morning hours of January 1, 2005, Chicago Police
Officers Ronald Coleman and Joshua Wallace responded
to a radio call of shots fired in their patrol area. After
exiting his vehicle, Coleman heard a series of gunshots and
saw the defendant, Willie Dabney, firing a handgun
approximately 30-40 yards away. With Coleman in pursuit
and closing the distance between them, Dabney ran toward
a nearby apartment building, firing two shots into the air
along the way. After entering the building through a
locked gate, Dabney dropped his gun and entered a second-
floor apartment. Around the same time, Wallace arrived
and helped Coleman climb onto the second-floor landing
of the apartment building, where Coleman recovered
Dabney’s gun. Coleman then gained entry into the apart-
ment he had seen Dabney enter and found Dabney hid-
ing under the bed. Dabney was arrested and pleaded
guilty to a state charge relating to his possession of the
gun Coleman had recovered. He was then charged with
one federal count of being a felon in possession of a fire-
arm in violation of 18 U.S.C. § 922(g)(1).
  Prior to trial on the federal charge, Dabney moved in
limine to bar any reference to his state-court guilty plea,
arguing that admission of the plea would be unfairly
prejudicial. The district court held that the government
could not reference the guilty plea itself but could intro-
duce evidence that Dabney had previously admitted
under oath that he possessed the firearm on the date in
question. Based on this ruling, the parties entered into
the following stipulation:
    In 2005, while under oath and with the assistance and
    presence of an attorney, the defendant, Willie Pierre
    Dabney, admitted that on January 1st, 2005, he
    possessed the same firearm as charged in the indict-
No. 06-2192                                              3

   ment; namely, A Glock model 17 C, bearing serial
   number CBT749, and that at the time of his possession
   the defendant had previously been convicted of a
   felony offense.
  On the day trial was scheduled to begin, the govern-
ment disclosed in response to a recent discovery request
that it had just learned of an individual who had made two
allegations of misconduct against Officers Coleman and
Wallace. Both concerned incidents in which the officers
allegedly released individuals from traffic stops in ex-
change for cash. The government indicated it had no
substantiating information but requested an extended
continuance to investigate further. Because jury selec-
tion had already begun, the district court granted only a
one-day continuance and instructed the government to
look for any other complaint material in its possession
regarding the two officers.
  After the one-day recess, the government informed the
court that it had 29 or 30 complaint registers for the two
officers. Only one complaint was substantiated, against
Coleman for a self-reported instance of inattention to duty
during a narcotics inventory proceeding. There was also
one pending investigation regarding a complaint that
Wallace had struck someone on the head with a gun while
executing a search warrant and that $2950 in cash had
gone missing after the search. The government took the
position that it need only turn the remaining complaints
over for in camera review since they had all been deemed
unsubstantiated. The district court held that the sus-
tained and pending complaints were inadmissible ex-
trinsic evidence of prior conduct under Rule 608 of the
Federal Rules of Evidence. Dabney then asked to review
all of the remaining complaint registers, or at least to
have the court review them in camera. Based on the
government’s representation that the remaining com-
4                                             No. 06-2192

plaints were unsubstantiated, the district court denied
both requests.
  The trial then continued, and the government introduced
the stipulation regarding Dabney’s prior admission to
possessing the gun, along with testimony from Coleman
and Wallace regarding the events on the night in question.
The jury found Dabney guilty; he was sentenced to 120
months in prison, the statutory maximum for his offense.
Dabney now appeals both the conviction and the sentence.


                     II. Discussion
A. Admission of Stipulation
  Dabney first contends that the district court erred by
allowing into evidence his admission, in the prior state-
court proceeding, that he possessed the gun in question on
the night in question. He argues that his prior admission
was inadmissible because it created a danger of “unfair
prejudice [or] confusion of the issues.” See FED. R.
EVID. 403. We review a district court’s ruling on the
admissibility of evidence for abuse of discretion. United
States v. Aldaco, 

, 985 (7th Cir. 2000).
   The parties entered into the stipulation regarding
Dabney’s state-court admission after the district court’s
split ruling on Dabney’s motion in limine, excluding
evidence of the guilty plea itself but allowing evidence of
Dabney’s state-court admission to possessing the gun. The
admission was certainly compelling evidence of Dabney’s
guilt, but there was nothing unfairly prejudicial about it.
“ ‘Unfair prejudice’ refers to ‘the capacity of some
concededly relevant evidence to lure the fact finder into
declaring guilt on a ground different from proof specific
to the offense charged.’ ” United States v. Coleman,

, 1062 (7th Cir. 1999) (citing Old Chief v.
United States, 

, 180 (1997))). It is hard to
No. 06-2192                                               5

imagine proof more specific to the offense charged than the
defendant’s own admission under oath to the essential
facts constituting the offense.
  The district court diminished any possibility of confusion
regarding the separate state and federal judicial proceed-
ings by taking the unnecessary precaution of excluding
any reference to the fact that Dabney’s statements were
made during a guilty plea hearing. See United States v.
Haddad, 

, 1258 (7th Cir. 1993) (state-court
guilty pleas are admissible as party admissions in subse-
quent federal court proceedings). The district court was
well within its discretion in admitting the evidence of
Dabney’s state-court admission.


B. Brady Allegations
  Dabney maintains that his rights under Brady v.
Maryland, 

(1963), were violated by the district
court’s failure either to further investigate the complaints
pending against the testifying officers or to require the
government to turn over all of the unsubstantiated com-
plaint registers in its possession. We review a district
court’s determination that disputed evidence need not be
produced under Brady for abuse of discretion. United
States v. O’Hara, 

, 569 (7th Cir. 2002).
  The Supreme Court held in Brady that “the suppres-
sion by the prosecution of evidence favorable to an ac-
cused upon request violates due process where the evi-
dence is material either to guilt or to 

. This holding places no investigative obligation on
courts, but rather only mandates that the prosecution must
turn over all potentially exculpatory evidence in its
possession. 

Dabney’s first argument fails
because the district court was under no independent
duty to further probe or investigate the pending com-
6                                            No. 06-2192

plaints against the officers that were identified by the
government. See, e.g., United States v. Mitchell, 

, 908 (7th Cir. 1999) (collecting cases rejecting the
notion that Brady places discovery obligations upon
courts).
  We turn, then, to Dabney’s claim that the district court
should have ordered the disclosure of the remaining
complaint registers, either to Dabney directly or to the
court for in camera review. Dabney can only demonstrate
a Brady violation if the evidence the government allegedly
suppressed “is both favorable to the accused and material
to the issue of guilt or punishment.” United States v.
Bastanipour, 

, 1181 (7th Cir. 1994). “There
is never a real ‘Brady violation’ unless the nondisclosure
was so serious that there is a reasonable probability
that the suppressed evidence would have produced a
different verdict.” Strickler v. Greene, 

, 281
(1999).
  Although the prosecution’s Brady obligation extends to
impeachment evidence, Giglio v. United States, 

(1972), Dabney provides no support for his assertion
that the remaining, unsubstantiated complaint registers
contained admissible impeachment evidence. Because
extrinsic evidence cannot be introduced to prove specific
conduct attacking a witness’s credibility, FED. R. EVID.
608(b), the complaint registers would have been inadmissi-
ble to rebut the officers’ denials of the allegations. See
United States v. Veras, 

, 1375 (7th Cir. 1995)
(suppressed misconduct allegation against police officer
witness was not material because inadmissible under
Rule 608(b)).
  Moreover, although the district court decided in camera
review was unnecessary, the government’s offer to turn the
documents over for such review “negates any argument
that the government suppressed favorable or material
No. 06-2192                                                 7

information.” 

. Finally, given
Dabney’s own admission to possessing the firearm, there
is no serious possibility that disclosure of the com-
plaints—whatever their content—would have led to a
different verdict. Accordingly, the district court did not
abuse its discretion by denying Dabney’s Brady requests.


C. Sufficiency of the Evidence
  Dabney also challenges the sufficiency of the evidence
to support his conviction. We review a sufficiency of the
evidence challenge “by considering the evidence in the light
most favorable to the government, deferring to the credibil-
ity determinations of the jury, and . . . overturn[ing] a
verdict only when the record contains no evidence, regard-
less of how it is weighed, upon which a rational trier of fact
could find guilt beyond a reasonable doubt.” United States
v. Cummings, 

, 397 (7th Cir. 2005). On this
record, a challenge to the sufficiency of the evidence is
frivolous. Dabney’s admission under oath to possessing the
gun was corroborated by the testimony of the officers who
chased and apprehended him. Dabney identifies only
minor, immaterial inconsistencies in the officers’ testi-
mony. The evidence supporting this conviction is over-
whelming.


D. Sentencing
  Dabney was sentenced to 120 months, which is the
statutory maximum for the offense and falls within the
advisory sentencing guidelines range of 100-125 months.
Dabney does not challenge the guidelines calculation, but
rather maintains the sentence was not reasonable be-
cause the district court failed to adequately consider the
factors set forth in 18 U.S.C. § 3553(a). The Supreme Court
has recently held that appellate courts may apply a
8                                               No. 06-2192

presumption of reasonableness to sentences imposed
within a properly calculated guidelines range. Rita v.
United States, 

(2007). In doing so, the
Court noted that it is important for a sentencing judge to
set forth his reasons for imposing a particular sentence “to
satisfy the appellate court that he has considered the
parties’ arguments and has a reasoned basis for exercis-
ing his own legal decisionmaking authority.” 

  Contrary to Dabney’s assertion, the district court’s
sentencing determination was adequately explained and
soundly reasoned. The court cited numerous § 3553(a)
factors, including Dabney’s nine previous convictions for
conduct ranging from drug possession to aggravated
battery of a police officer, the failure of prior terms of
imprisonment to alter his criminal behavior, and the
danger he caused by firing his weapon on the night in
question. The maximum sentence imposed here was
amply justified and entirely reasonable.
  Finally, in his reply brief Dabney raised for the first time
the argument that he would have pleaded guilty had the
government not mistakenly asserted prior to trial that it
would seek to have him sentenced as an armed career
criminal. Accordingly, he asserts, he would have received
a three-point reduction for acceptance of responsibility.
This is the first mention of this argument, which Dabney
provides no legal authority to support. Because the
argument was not raised or developed in the opening
brief, it is waived. See United States v. Hook, 

,
310 (7th Cir. 1999).
                                                  AFFIRMED.
No. 06-2192                                         9

A true Copy:
      Teste:

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




               USCA-02-C-0072—8-2-07