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

No. 07-2804
ROBERT L. PEALS,
                                                 Plaintiff-Appellant,
                                  v.

TERRE HAUTE POLICE DEPARTMENT,
GEORGE A. RALSTON III, Terre Haute
Police Chief, in his official capacity,
TREY GILBERT, Terre Haute
Police Officer, et al.,
                                              Defendants-Appellees.
                          ____________
             Appeal from the United States District Court
      for the Southern District of Indiana, Terre Haute Division.
                No. 05 C 223—Richard L. Young, Judge.
                          ____________
        ARGUED JUNE 6, 2008—DECIDED JULY 25, 2008
                          ____________


  Before BAUER, RIPPLE and MANION, Circuit Judges.
  RIPPLE, Circuit Judge. Robert Peals filed this action under
42 U.S.C. § 1983 against the Terre Haute Police Depart-
ment and several individual police officers. Mr. Peals
alleged that the defendants had performed an unlawful
search, falsely arrested him, initiated a retaliatory pros-
ecution against him and used excessive force against him.
Before trial, the district court granted the defendants’
2                                              No. 07-2804

summary judgment motion with respect to Mr. Peals’
unlawful search, false arrest and retaliatory prosecution
claims. The court also dismissed his claims against all
of the defendants except Officers Trey Gilbert and Curt
Brinegar. The remaining excessive-force claim proceeded
to trial, and the jury found in favor of the defendants.
Mr. Peals timely appealed the district court’s grant of
summary judgment on two of his claims and two of the
court’s rulings at trial. For the reasons discussed in this
opinion, we affirm the judgment of the district court.


                             I
                    BACKGROUND
                            A.
  On September 15, 2003, Mr. Peals was arrested in his
garage by a number of Terre Haute police officers from the
Street Crimes Unit, a unit used to perform special tasks
including high-risk arrests, narcotics arrests and narcotics
information gathering. Among these officers were two K-9
officers who were detailed at that time to the Street
Crimes Unit. The police officers had a warrant for Mr.
Peals’ arrest on charges of battery resulting in injury and
invasion of privacy, but they did not possess a search
warrant for his home. After the officers took Mr. Peals into
custody, Mr. Peals observed Officer Brinegar, several
other officers and the K-9 units looking around the
garage “as if [they] were searching for something.” R.77,
Ex. C. In addition, Mr. Peals observed Officer Brinegar
enter Mr. Peals’ house.
 In an unrelated incident, on January 15, 2005, Officer
Gilbert arrested Mr. Peals in a restaurant parking lot
No. 07-2804                                                     3

pursuant to a bench warrant for failure to pay child
support and failure to appear in court.1 On that evening,
Officer Gilbert was providing police security at a restau-
rant and was wearing a t-shirt printed with a badge and
the word “POLICE.” When Mr. Peals entered the restau-
rant, he was stopped by Officer Gilbert, who recognized
him from the Vigo County Sheriff’s Department Active
Warrant List. Officer Gilbert told Mr. Peals that there
was a warrant for Mr. Peals’ arrest. While Officer
Gilbert called the police station to check the status of
the warrant, Mr. Peals said that he did not believe that
Officer Gilbert had a warrant and walked to the parking
lot. Officer Gilbert pursued and arrested him there. As a
result of this incident, Mr. Peals was charged with re-
sisting arrest.


                               B.
  Following his 2005 arrest, Mr. Peals filed a section 1983
claim against the Terre Haute Police Department, the Police
Chief in his individual capacity, and eight known and
additional unknown officers. Alleging violations of his
rights under the First, Fourth, Eighth and Fourteenth
Amendments, the suit included four claims based on the


1
   Mr. Peals contends that this arrest occurred after he had filed
a complaint against Officer Gilbert, but there is no admissible
evidence in the record that supports his contention. The only
evidence in the record related to this point is a document titled
“Complaint Against Police Officer” that is uncertified and that
is dated January 4, 2005. R.77, Ex. I. There is no evidence in the
record that Mr. Peals filed the complaint, that it ever was
received by the Police Department, or that Officer Gilbert
was aware of the complaint.
4                                              No. 07-2804

2003 and 2005 incidents: unlawful search, false arrest,
initiation of a retaliatory prosecution and excessive force.
The defendants moved for summary judgment on all
claims. The district court granted the motion as to Mr.
Peals’ unlawful search, retaliatory prosecution and false
arrest claims but denied the motion on his excessive force
claims. Before trial, the district court also dismissed the
claims against all of the defendants except Officers
Brinegar and Gilbert.
   Mr. Peals requested Officer Gilbert’s and Officer
Brinegar’s personnel files. The district court examined the
files in camera and determined that they did not con-
tain information necessary to Mr. Peals’ case and there-
fore would not be divulged. Mr. Peals did not object to the
district court’s determination; in response to the deter-
mination, his counsel simply replied, “Okay.” Tr. at 15.
  The district court also denied Mr. Peals’ request to
call Officer Peter Tanoos as a rebuttal witness. The court
agreed with the defendants that Officer Tanoos’ testimony
would be improper rebuttal testimony because it should
have been introduced during Mr. Peals’ case in chief.
 The jury found in favor of the officers on all claims.
Mr. Peals timely appealed.


                            II
                      DISCUSSION
                            A.
  Mr. Peals contends that the district court improperly
granted summary judgment on his claims of retaliatory
prosecution and unlawful search. We review de novo
the district court’s decision to grant a motion for sum-
No. 07-2804                                                 5

mary judgment and may affirm that decision on any
ground found in the record. Hull v. Stoughton Trailers, LLC,

, 951 (7th Cir. 2006). Summary judgment is
appropriate if “the pleadings, depositions, answers to
interrogatories, and admissions on file, together with the
affidavits, if any, show that there is no genuine issue as
to any material fact and that the moving party is entitled
to a judgment as a matter of law.” Keck Garrett & Assocs. v.
Nextel Commc’ns, Inc., 

, 483 (7th Cir. 2008); Fed.
R. Civ. P. 56(c).


1. Retaliatory Prosecution
  Mr. Peals contends that the district court improperly
granted summary judgment on his claim that Officer
Gilbert initiated a retaliatory prosecution against him. Mr.
Peals submits that Officer Gilbert arrested him and then
influenced the prosecutor into charging him with re-
sisting arrest because of the complaint that he contends
that he submitted against Officer Gilbert on January 4,
2005.
  An individual may not be subject to criminal prosecu-
tion for exercising his right to free speech. Hartman v.
Moore, 

, 256 (2006). If an individual is sub-
jected to criminal prosecution in retaliation for constitu-
tionally protected speech and “nonretaliatory grounds
are in fact insufficient to provoke the adverse conse-
quences,” then instigation of the retaliatory prosecution “is
subject to recovery as the but-for cause of official action
offending the Constitution.” 

who is
subjected to such a retaliatory prosecution therefore may
bring a section 1983 claim against an official “who may
have influenced the prosecutorial decision but did not
himself make it, and the cause of action will not be
6                                              No. 07-2804

strictly for retaliatory prosecution, but for successful
retaliatory inducement to prosecute.” 

To suc-
ceed on such a claim, the plaintiff must show a causal
connection between the official’s retaliatory animus and
a subsequent injury in a retaliation action. 

He
“must show that the nonprosecuting official acted in
retaliation, and must also show that [the official] in-
duced the prosecutor to bring charges that would not have
been initiated without his urging.” 

“Thus, the
causal connection required here is . . . between the re-
taliatory animus of one person and the action of another.”

also must plead and prove, as an ele-
ment of his case, that there existed no probable cause to
support the underlying charge. 

  The district court granted the defendants’ motion for
summary judgment on Mr. Peals’ retaliatory prosecution
claim because it found that there was no evidence that
Officer Gilbert had induced the prosecutor to file resisting
arrest charges against Mr. Peals. Mr. Peals offers no
evidence, at summary judgment or on appeal, that Officer
Gilbert “induced the prosecutor to bring charges that
would not have been initiated without his urging.” See 

He relies only on the fact that Officer Gilbert
arrested him and that he subsequently was charged
with resisting arrest.
   Additionally, with respect to the underlying complaint of
police misconduct that allegedly induced the retalia-
tion, the record contains no admissible evidence that
Mr. Peals ever filed a complaint against Officer Gilbert,
that the Police Department ever received such a com-
plaint or that Officer Gilbert was aware of a complaint.
The only evidence related to such a complaint is a form
titled “Complaint Against Police Officer” that is uncerti-
No. 07-2804                                                7

fied. Under Federal Rule of Evidence 901, evidence must
be authenticated as a condition precedent to its admissi-
bility. Fed. R. Evid. 901(a). Public records or reports
such as Mr. Peals’ alleged complaint against Officer
Gilbert may be authenticated by showing evidence that
the writing “is from the public office where items of this
nature are kept.” Fed. R. Evid. 901(b)(7). Mr. Peals has
offered no evidence “sufficient to support a finding that
the matter in question is what its proponent claims.” Fed.
R. Evid. 901(a).
  The record contains no admissible evidence of retalia-
tory animus on the part of Officer Gilbert or of Officer
Gilbert’s influencing the prosecutor’s decision to charge
Mr. Peals with resisting arrest. The district court therefore
properly granted summary judgment for the officers on
this claim. See 

(holding that the
plaintiff “must show that the nonprosecuting official
acted in retaliation, and must also show that [the official]
induced the prosecutor to bring charges that would not
have been initiated without his urging”).


2. Unlawful Search
  The Fourth Amendment protects the right of the people
“to be secure in their persons, houses, papers, and effects,
against unreasonable searches and seizures.” U.S. Const.
Amend. IV. With few exceptions, the Fourth Amendment
prohibits the warrantless entry of a person’s home to
make an arrest or to conduct a search. Kyllo v. United
States, 

, 31 (2001). “A ‘search’ occurs when an
expectation of privacy that society is prepared to con-
sider reasonable is infringed.” United States v. Brock, 

, 696 (7th Cir. 2005) (quoting United States v.
Jacobsen, 

, 113 (1984)).
8                                                No. 07-2804

  One exception to the Fourth Amendment’s prohibition on
warrantless searches of a person’s home is a search inci-
dent to arrest, an exception first recognized in Chimel v.
California, 

(1969). Under this exception,
police officers may, incident to arrest, conduct a plenary
search of the arrestee’s person and the area within his
immediate control, that is, “the area from within which
he might gain possession of a weapon or destructible
evidence.” 

  Another such exception is the protective sweep, first
described in Maryland v. Buie, 

, 331 (1990).
Under the protective sweep exception, officers may,
incident to arrest and “as a precautionary matter and
without probable cause or reasonable suspicion, look in
closets and other spaces immediately adjoining the place
of arrest from which an attack could be immediately
launched.” 

A search beyond those parameters
is justified when there are “articulable facts which, taken
together with the rational inferences from those facts,
would warrant a reasonably prudent officer in believing
that the area to be swept harbors an individual posing
a danger to those on the arrest scene.” Id.; Leaf v. Shelnutt,

, 1086 (7th Cir. 2005). It is important to
note that a protective sweep is “not a full search of the
premises, but may extend only to a cursory inspection
of those spaces where a person may be found.” 

; 

. The justification for
a protective sweep is to protect “the safety of police
officers, who have an interest in ensuring their safety
when they lawfully enter a house. That interest justifies
their ensuring that the dwelling does not harbor another
person who is dangerous and who unexpectedly could
launch an attack.” 

(alteration omitted)
(internal quotation marks omitted).
No. 07-2804                                                9

  Mr. Peals contends that the district court improperly
granted summary judgment on his claim that the defen-
dants’ search of his garage and home was unreasonable.
He submits that the warrantless search of his garage and
home was not justified either as a protective sweep or as
a search incident to arrest.2 He makes two specific con-
tentions: (1) that the search was unreasonable because
it exceeded the limits of the protective sweep and
search incident to arrest exceptions, and (2) that the
search was unreasonable because it involved K-9 units.
We shall address each of these contentions.
  First, Mr. Peals submits that the search was unrea-
sonable because the officers did more than conduct a
cursory visual inspection of those places in which a
person might be hiding. The evidence in the record con-
tradicts this contention. Mr. Peals stated in his affidavit
that, after the officers took him into custody, he observed
Officer Brinegar and several other officers with K-9 units
looking around the garage “as if [they] were searching
for something.” R.77, Ex. C. In addition, Mr. Peals ob-
served Officer Brinegar enter Mr. Peals’ house. 

facts in the light most favorable to Mr. Peals, he
has not shown that the officers conducted an unconstitu-
tional search. His version of the events is consistent with
the limitations on a valid protective sweep. The officers
visually inspected the area in which Mr. Peals was
arrested and entered an immediately adjoining space in
which other persons might be located and from which
they could launch an attack. See 

.
Notably, Mr. Peals does not allege that any officer opened


2
  It is undisputed that the officers had and executed a valid
arrest warrant for Mr. Peals.
10                                              No. 07-2804

or otherwise manipulated anything in the garage or
house, or that the limited search extended beyond a brief
visual inspection of the areas immediately adjoining the
garage where he was arrested. See 

a
reasonable suspicion or probable cause, the undisputed
facts show that the search conducted by the officers was
reasonable as a protective sweep. See id.; see also 

.
  Second, Mr. Peals contends that the presence of K-9
units in his garage made the search unreasonable. We
cannot accept this contention. As a general rule, K-9
units trained to protect officers and apprehend suspects
may accompany police officers. See, e.g., United States v.
Lawshea, 

, 860 (7th Cir. 2006) (holding that
the use of a police dog to assist in effecting a Terry stop
was reasonable when the person ran from the officer
and ignored the officer’s orders to stop). We have also
held that K-9 units trained to detect contraband do not
conduct a search when they sniff in an area where they
are lawfully present. 

.
  As we have noted earlier, the officers and the K-9 units
were lawfully present in Mr. Peals’ garage. Moreover,
there is no evidence in the record regarding the purpose
or detection capabilities of the K-9 units. The reasonable
inference therefore is that the K-9 units, which are a
standard part of the Street Crimes Unit, were trained
either to protect the officers and apprehend suspects or
to detect narcotics.3 Without a material issue of fact on the



3
  Officer Brinegar testified that the Street Crimes Unit per-
formed special tasks, including high-risk arrests, narcotics
arrests and narcotics information gathering. Tr. at 17-19.
No. 07-2804                                              11

question of whether the K-9 units used in this search
were trained to search for non-contraband items, we
need not reach to resolve the question of whether,
when lawfully inside of a home, the use of a K-9 unit
trained to sniff for non-contraband items is a search. See

a sniff by a dog trained to search for
drugs was not a search “because it detected only the
presence of contraband and did not provide any infor-
mation about lawful activity over which Brock had a
legitimate expectation of privacy”); see also Illinois v.
Caballes, 

(2005); 

, 40.
  The district court therefore properly granted summary
judgment to the defendants on Mr. Peals’ claim of unlawful
search.


                            B.
  Mr. Peals also contends that, in conducting the trial on
the excessive force claim, the district court abused its
discretion when it prevented him from calling a wit-
ness and when it reviewed the officers’ personnel files
in camera without granting him access to the files. We
review for abuse of discretion a district court’s decisions
regarding rebuttal evidence, United States v. Grintjes,

, 879 (7th Cir. 2001), and discovery, United
States v. Phillips, 

, 277 (7th Cir. 1988).


1. Rebuttal Witness
  Mr. Peals submits that the district court abused its
discretion when it refused to permit him to call Officer
Peter Tanoos as a rebuttal witness. Officer Tanoos would
have testified about one of Mr. Peals’ prior arrests. Al-
12                                              No. 07-2804

though the substance of Mr. Tanoos’ proposed testimony
was not made known to the district court, Mr. Peals
contends before us that Officer Tanoos would have
testified that the charges in that incident were fabricated.
Mr. Peals further contends, on appeal only, that Officer
Tanoos’ testimony would have been relevant to the
other officers’ attitudes toward him. He contends that the
district court abused its discretion by refusing to permit
Officer Tanoos to testify as a rebuttal witness.
  Mr. Peals testified during his case in chief regarding
some of his previous encounters with the police depart-
ment involved in this case. He also testified about the
cases underlying the arrest warrants that the officers
executed in 2003 and 2005, which generated the claims
in this case. On cross-examination, counsel for the offi-
cers elicited, without objection, information from Mr.
Peals about the particular facts and circumstances of his
other encounters. Mr. Peals did not provide more infor-
mation about these arrests during his case in chief by
seeking the admission of other evidence. Then, after
the defendants had presented their case, Mr. Peals
sought to introduce testimony regarding those issues
raised when he had been cross-examined during his case
in chief. After a discussion in chambers, the following
exchange on the record among court and counsel ad-
dressed this issue:


     THE COURT: All right. Mr. Lenkowsky, do you wish
     to make some type of record?
     MR. LENKOWSKY: Yes, your Honor. In chambers
     conference yesterday, I requested calling a Pete Tanoos
     as a rebuttal witness. At that point you indicated you
No. 07-2804                                              13

    would not allow me to do that. Our argument is
    basically we only presented--on our case the only
    evidence we presented was that he was found not
    guilty. We do not go into the factual circumstances.
    Mr. Drummy, if I recall correctly, actually did go into
    some of the factual circumstances, so at that point
    we think that rebuttal by calling Mr. Tanoos, who
    was involved in the investigation, would be proper.
    THE COURT: Mr. Drummy?
    MR. DRUMMY: The evidence that I offered with
    regard to the facts of the crime was offered during the
    plaintiff’s case in chief without objection. It would be
    inappropriate to allow rebuttal. If he wished to call
    Mr. Tanoos after that testimony is offered, then Mr.
    Tanoos should have been called in this case-in-chief.
    THE COURT: That’s correct. I believe that’s what our
    discussion was in chambers last evening, was centered
    around the point that Mr. Drummy did make those
    points and allegations in cross examination during the
    plaintiff’s case. It would be improper rebuttal.
    MR. LENKOWSKY: Okay.
Tr. at 524-25.
  “The proper function of rebuttal evidence is to contra-
dict, impeach or defuse the impact of the evidence
offered by an adverse party.” 

(internal quotation marks omitted). Testimony offered only
as additional support to an argument made in a case in
chief, if not offered “to contradict, impeach or defuse
the impact of the evidence offered by an adverse party,”
is improper on rebuttal. See 

determination
to exclude rebuttal testimony is not an abuse of discre-
14                                              No. 07-2804

tion absent a showing of prejudice. Nanda v. Ford Motor
Co., 

, 223 (7th Cir. 1974); Fed. R. Evid. 103
(“Error may not be predicated upon a ruling which ad-
mits or excludes evidence unless a substantial right of
the party is affected, and . . . the substance of the evid-
ence was made known to the court by offer or was ap-
parent from the context within which questions were
asked.”). If the party objecting to the exclusion of the
evidence fails to make a proper offer of proof, “there is
no basis for a finding of prejudice.” 

;
see also Fed. R. Civ. P. 61 (“Unless justice requires other-
wise, no error in admitting or excluding evidence . . . is
ground for granting a new trial. . . . At every stage of
the proceeding, the court must disregard all errors and
defects that do not affect any party’s substantial rights.”).
  On this record, we cannot say that the district court
abused its discretion in refusing to permit the testimony.
The court certainly was justified in accepting the represen-
tation of the defendants, which Mr. Peals did not ques-
tion at the time, that the evidence that Mr. Peals sought
to rebut had been offered during the plaintiff’s case in
chief without objection. The record before us does not
provide any basis for finding that representation to have
been inaccurate; the testimony that Mr. Peals sought to
introduce on rebuttal was responsive to the defendants’
cross-examination of him during his case in chief, not to
the defendants’ case. Because the testimony was clearly
not an appropriate subject for rebuttal, the district court
clearly did not abuse its discretion in excluding it. See

. The district court, which is far
closer than we to matters concerning the presentation of
evidence, certainly did not err clearly when it accepted
the Government’s argument and excluded the testimony.
No. 07-2804                                             15

See 

; Fed. R. Civ. P. 61. Mr. Peals,
moreover, did not make known to the district court, at the
time of its ruling, the substance of Officer Tanoos’ pro-
posed rebuttal testimony or how that testimony
would have related to the substance of his excessive
force claims. He therefore has failed to demonstrate
prejudice because he failed to make a sufficient offer of
proof to the district court.


2. Personnel Files
  Mr. Peals contends that the district court abused its
discretion by reviewing in camera the personnel files of
Officer Gilbert and Officer Brinegar and by refusing to
turn those files over to him. The only evidence con-
cerning this issue is the following statement by the trial
court:
   All right. The court has examined the personnel files
   of the two defendant police officers and there is noth-
   ing in those files that indicate any discipline or any
   type of complaints regarding excessive force. There
   is a notation in there about one of them being late
   for court, and there is some information, also in there
   about doing a good job.
Tr. at 15. Following this statement, Mr. Peals’ counsel
said, “Okay.” 

files of the two officers
are not part of the record.
  Mr. Peals contends that the district court abused its
discretion when it reviewed the officers’ personnel files
in camera instead of turning the files over to him. “Gener-
ally, the decisions whether to conduct an in camera
review of government files in appropriate cases, whether
16                                               No. 07-2804

to require discovery of materials contained therein, and
in what form such materials should be produced are
committed to the sound discretion of the district judge.”

.
   Mr. Peals failed to object to the district court’s decision
to review the files in camera instead of making them
available to him. Neither did he make any offer of proof
to the district court or so much as “hint that impeaching
material was contained” in the files. See 

failed to object and make an offer of proof, there is no
basis for a finding of prejudice, which is necessary for us
to hold that the district court abused its discretion. Cf.

; see also Fed. R. Evid. 103(a) (“Error
may not be predicated upon a ruling which admits or
excludes evidence unless a substantial right of the party
is affected.”); Fed. R. Civ. P. 61 (“Unless justice requires
otherwise, no error in admitting or excluding evidence . . .
is ground for granting a new trial.” (emphasis added)).


                        Conclusion
   The district court properly granted summary judg-
ment for the defendants on Mr. Peals’ claims of retalia-
tory prosecution and unlawful search, and it did not
abuse its discretion when it excluded certain rebuttal
testimony and reviewed in camera the defendants’ person-
nel files. Accordingly, the judgment of the district court
is affirmed.
                                                   AFFIRMED


                    USCA-02-C-0072—7-25-08