Joseph R. Anderer, Jr. is a former Milwaukee police officer who was arrested for physically abusing a child. Though he was not prosecuted, Anderer was terminated following an internal affairs investigation into this incident. Anderer sued the police chief, other officers involved in his arrest, and the City of Milwaukee for violating his Fourth Amendment rights by arresting him without probable cause, and for terminating his employment after his representative spoke out against the arrest and Anderer filed this lawsuit. Finding that probable cause existed at the time Anderer was arrested and that the speech at issue was not protected by the First Amend*1046ment, the district court granted summary judgment to defendants. We agree with the district court’s decision and affirm.
I. BACKGROUND1
On April 17, 2001, Milwaukee police officer Joseph Anderer and several other officers arrested four juveniles for burglarizing a boat. After the juveniles were handcuffed, and while they were being escorted to the patrol cars, one 12-year-old boy (whom we will call JR) started shouting that one of the officers who was escorting him to the car, Officer Jeffrey Cook, was touching him on the buttocks and trying to rape him. Three of the juveniles were then transported to the police station by Officer Cook and his partner Officer Jeffrey Logan, while Sergeant Michael Jones, Officer Janice Shoman, Anderer, and JR remained behind. JR was placed in a patrol car and driven to the station by Anderer, while Sgt. Jones interviewed witnesses before returning to the station.
Once Anderer and JR arrived at the station, several officers noticed that JR was bleeding from the nose and mouth and had blood on his clothing. Lieutenant Kim Stack asked JR what happened, and he said that Anderer hit him in the face. When Sgt. Jones heard Lt. Stack talking to JR, he asked JR what had happened to him, and JR said that Anderer hit him. Sgt. Jones then asked Anderer how JR had received the bloody nose, to which Anderer responded, “how would I know ... I just transported him.” Several other officers also interviewed JR, including Lt. Mary Hoerig and Detective William Smith of the Internal Affairs Department (IAD), and he told them all that he had been hit in the face by Anderer.
When Det. Smith interviewed him, JR explained the details of the burglary for which he had been arrested. JR said that when he was placed in Anderer’s patrol car, Anderer did not immediately shut the door, but instead asked him questions about what JR had been saying Officer Cook did to him. JR then said that when he told Anderer that Officer Cook nudged him in the buttocks with a flashlight, An-derer started yelling at him and told him he shouldn’t be making up “bullshit lies.” JR told Det. Smith that he got smart with Anderer, ignored him, and looked away. JR stated that when he turned back to face Anderer, Anderer struck him in the face and caused his nose and mouth to bleed.2 JR added that while he was being transported to the station, Anderer was yelling at him and saying “do you understand me?”, and at one point stopped the car, opened the back door, and said he was going to “whip [JR’s] ass.” JR said he thought they were alone when all of this occurred and did not know if anyone else had witnessed it.
While others were talking to JR, Officer Cook contacted JR’s mother to inform her that JR had been arrested. JR’s mother admitted that she was not surprised that JR had been arrested for burglary and advised Officer Cook that JR was taking several prescription medications, including two that Officer Cook recognized as pills to “help control a person’s mental state.” She also told him that JR had not taken his medication that day and needed to be released from custody as soon as possible. Officer Cook informed Sgt. Brunson and IAD Detectives Harrison and Smith that he had been in contact with JR’s mother and that JR had been prescribed a variety *1047of drugs that he had not taken all day and should be processed as soon as possible.
Det. Smith attempted to interview Officers Cook and Logan about the facts surrounding JR’s arrest and the cause of his injuries, but they refused to give a statement without police union representatives present. Det. Smith interviewed Sgt. Jones, who indicated that he was the last person to leave the scene of the arrest and that he had not seen any sign of injury to JR. Sgt. Jones informed Det. Smith that he saw no blood on JR at the scene, and probably would not have noticed the cuts on the inside of JR’s lips, but there was enough blood on his shirt at the station that he would have noticed it if it had been there earlier. Sgt. Jones then relayed to Det. Smith the substance of his interview with JR, in which JR detailed the events that resulted in his arrest and the interactions with Anderer that resulted in JR’s bloody nose and lip.
Detectives Smith and Harrison then interviewed Officer Janice Shoman, who also provided details about JR’s arrest. She indicated that she left the scene to pursue another crime before JR was transported to the station, but before she left she saw Anderer with JR in the back of Anderer’s car. She could not recall if JR had handcuffs on, but did not see any physical confrontation between JR and Anderer. She stated that she did not see any blood or injury on JR,' and said she would have noticed if there had been blood on his shirt.
Anderer refused to give a formal statement without union representation, but at one point asked, “off the record,”3 “What did he say I hit him with?” When he was told by one officer that JR said he had punched him in the face, Anderer stated that he was a 200 pound man and if he had punched JR in the face it would have left bruises on JR. Anderer then let the investigating officers inspect his hands, but no photographs were taken, as there did not appear to be any marks or injuries on them. Anderer did not provide any explanation for how JR received the cuts and bloody nose. He did not indicate that there had been any force exercised in effecting the arrest, nor did he suggest that any kind of accident or incident had occurred on the way back to the station. Anderer states that during the course of his “off the record” conversations with them, Detective Harrison, Lt. Stack, and Officer Cook told him that they thought JR’s claim was bogus, to which Anderer responded to Officer Cook that he thought was going to get “Driebeled.”4
Lt. Hoerig placed a call to Milwaukee Police Chief Arthur Jones to apprise him of the situation. Chief Jones asked Lt. Hoerig if she thought there was probable cause to arrest Anderer for physical abuse of a child, in violation of Wis. Stat. § 948.03. Lt. Hoerig informed Chief Jones that she believed there was probable cause to arrest, and the investigating detectives concurred. Chief Jones asked Lt. Hoerig if she would arrest Anderer if he were a private citizen, and Lt. Hoerig indicated that she would. Chief Jones then ordered Anderer’s arrest.
*1048Immediately following his arrest, Anderer was taken to the Milwaukee County Criminal Justice Facility, where he was held for twelve hours before being released without bail. That afternoon, April 18, Anderer appeared at the Deputy District Attorney’s office to make a statement, but because the union attorney was not present, his statement was to be rescheduled. On April 19, after being authorized by Anderer, union president Bradley De-Braska told a local TV station that Anderer was arrested without probable cause because of vindictiveness of the IAD Unit due to prior run-ins between Anderer and one of the IAD investigators, and the union was “hoping and praying” Anderer would sue the police department to correct these wrongs.
On June 7, the district attorney’s office decided not to pursue the criminal charges against Anderer with respect to JR’s accusation. At that time, a local Milwaukee television station reported that charges would not be pursued and that Anderer had retained an attorney to file a complaint against the Milwaukee Police Department and its police chief. On June 13, the reopened criminal investigation into JR’s allegations was closed and no further information was developed to further a potential prosecution. On June 19, Anderer was required to give a statement to the IAD for the purpose of a work-rule-violation investigation of his excessive use of force.
On July 2, Anderer filed suit in federal district court alleging violations of his civil rights for arresting him without probable cause with respect to JR’s accusation. On July 6, the IAD commander issued charges against Anderer alleging that he violated rules and regulations with respect to JR’s arrest, and in doing so he quoted from the allegations in Anderer’s complaint. On July 17, Chief Jones terminated Anderer’s employment, which Anderer has appealed to the City’s Fire and Police Commission. Anderer then filed an amended complaint, adding a count alleging that he was terminated in retaliation for exercising his First Amendment rights.
Defendants filed a motion for summary judgment, claiming that there was probable cause to arrest Anderer and that his First Amendment count failed to state a claim for relief. The district court granted summary judgment on Anderer’s Fourth and First Amendment claims, finding that there was probable cause for his arrest and the speech at issue concerned a private personal dispute that was not a “matter of public concern.” Anderer appeals.5
II. ANALYSIS
A. Probable Cause to Arrest
We review a district court’s grant of summary judgment de novo, and in doing so draw all reasonable inferences from the record in the light most favorable to Anderer, the non-movant. Woods v. City of Chicago, 234 F.3d 979, 986 (7th Cir.2000). This court discussed at length the standard for evaluating probable-cause-to-arrest challenges in § 1983 cases in Spiegel v. Cortese, 196 F.3d 717, 723 (7th Cir.1999), and Driebel v. City of Mil*1049waukee, 298 F.3d 622 (7th Cir.2002). Probable cause is “ ‘a commonsense determination, measured under a reasonableness standard.’ ” Spiegel, 196 F.3d at 723 (quoting Tangwall v. Stuckey, 135 F.3d 510, 519 (7th Cir.1998)). Probable cause exists if, at the time of the arrest, “ ‘the facts and circumstances within [the arresting officer’s] knowledge and of which she has reasonably ' trustworthy information would warrant a prudent person in believing that the suspect had committed or was committing an offense.’ ” Id. (quoting Qian v. Kautz, 168 F.3d 949, 953 (7th Cir.1999)).
In evaluating whether probable cause was reasonably determined, the court “must consider the facts as they would have reasonably appeared to the arresting officer ‘seeing what he saw, hearing what he heard’ at the time of the incident.” Driebel, 298 F.3d at 643 (quoting Richardson v. Bonds, 860 F.2d 1427, 1431 (7th Cir.1988)); Spiegel, 196 F.3d at 723 (“The existence of probable cause turns on the information known to the officers at the moment the arrest is made, not on subsequently-received information.”). “An officer’s belief in the existence of probable cause ‘need not be based on evidence sufficient to support a conviction, nor even a showing that the officer’s belief is more likely true than false.’ ” Driebel, 298 F.3d at 643 (quoting Woods, 234 F.3d at 996) (emphasis in original). Accordingly, “ ‘as long as a reasonably credible witness or victim informs the police that someone has committed, or is committing, a crime, the officers have probable cause to place the alleged culprit under arrest, and their actions will be cloaked with qualified immunity if the ar-restee is later found innocent.’ ” Spiegel, 196 F.3d at 723 (quoting Jenkins v. Keating, 147 F.3d 577, 585 (7th Cir.1998)). In reviewing a-probable cause determination, the court should consider whether the arresting officer “ ‘acted reasonably under settled law in the circumstances, not whether another reasonable, or more reasonable, interpretation of the events can be constructed several years after the fact.’ ” Id. (quoting Humphrey v. Staszak, 148 F.3d 719, 725 (7th Cir.1998)). “Moreover, this court has emphasized that once probable cause has been established, officials have ‘no constitutional obligation to conduct any further investigation in the hopes of uncovering potentially exculpatory evidence.’ ” Id. (quoting Eversole v. Steele, 59 F.3d 710, 718 (7th Cir.1995)).
With these standards in mind, we agree with the district court’s conclusion that probable cause to arrest existed at the time Anderer was arrested.6 In Wisconsin, a person physically abuses a child when he intentionally or recklessly “causes bodily harm to a child.” Wis. Stat. § 948.03. Here, JR arrived at the police station in Anderer’s sole custody and was bleeding from his nose and mouth with split lower and upper lips, and no police officer observed him in 'that condition at the time of his arrest or when he was *1050turned over to Anderer’s sole custody. JR told several police officers the same story: Anderer had hit him in the face when JR had gotten “smart” with Anderer.7 An-derer offered no explanation to the investigating officers for how JR’s injuries might otherwise have occurred, and appears only to have inquired about what JR claimed Anderer had hit him with. Given these circumstances—a 12-year-old’s injuries and bloody appearance, his consistency in reporting how he had been injured, and Anderer’s total failure to provide any explanation for the injuries when no other officer observed JR in that condition prior to turning him over to Anderer’s sole custody8—we believe the Milwaukee police officers had probable cause to believe that Anderer had intentionally or recklessly caused JR’s bodily injury. See Wis. Stat. § 948.03.
Anderer claims that JR was not a credible victim because (1) he had made other allegations about Officer Cook earlier that evening, and (2) the officers investigating JR’s claims knew JR was on medication for mental illness and had failed to take his pills that day. We disagree with Anderer’s conclusion with respect to both assertions. JR himself reported to the investigators that he had made allegations about Officer Cook and he explained that it was his repetition of those statements to Anderer that he believed prompted Anderer’s hostility and violence. As for JR’s failure to take his medication, the fact that the investigating officers knew about JR’s medication does not ipso facto negate JR’s credibility or require the officers to further investigate JR’s medical history to substantiate or refute his claim of abuse by Anderer, see Driebel, 298 F.3d at 643; Spiegel, 196 F.3d at 723. And the fact that investigators later learned that JR had previously been diagnosed with psychosis, paranoia, hallucinations, and self-mutilation is irrelevant to what the officers reasonably knew at the time they arrested Anderer. Spiegel, 196 F.3d at 723.9
Anderer further claims that no officers corroborated JR’s allegation and that no *1051effort was made to interview the other officers and citizen witnesses who were present at the time of the arrest. First, while Sgt. Jones and Officer Shoman could not corroborate JR’s allegation against An-derer, neither could they refute it, and both stated that JR was not bloody at the time he had been turned over to Anderer’s sole custody. Second, Sgt. Jones and Officer Shoman were interviewed, and there were efforts made to interview other officers; Officers Cook and Logan were asked to provide a statement prior to Anderer’s arrest, but they refused to do so without union representation. Notably, when Officers Cook and Logan finally agreed to give statements (very shortly after Anderer’s arrest), they could neither corroborate nor refute JR’s allegations. Furthermore, they could not explain JR’s bloodied condition, and both stated that JR had not been bloody at the time he was turned over to Anderer’s sole custody.10
Anderer also asserts that probable cause was lacking because two identification technicians (“ID techs”) who took photographs of JR’s injuries and appearance within hours of Anderer’s arrest believed that “there were no injuries on JR” or that the injuries were “very minor.” Anderer appears to believe that these ID techs should have been consulted by the officers investigating JR’s claims prior to arresting Anderer, but we fail to see why this would be necessary when the investigating officers themselves regularly investigate batteries against persons and are capable of assessing the nature and possible cause of injuries. And once those officers determined that probable cause had been established, they had “ ‘no constitutional obligation to conduct any further investigation in the hopes of uncovering potentially exculpatory evidence? ” Spiegel, 196 F.3d at 723 (quoting Eversole, 59 F.3d at 718). Furthermore, one ID tech -did not photograph JR until after Anderer had already been .arrested, and so would have had nothing to contribute to the probable cause determination prior to his arrest, and the other ID tech’s photographs were not developed until after Anderer’s arrest.11
*1052Finally, Anderer points to other occurrences after his arrest as evidence to support his argument that probable cause did not exist. Anderer challenges JR’s credibility by arguing that the Deputy District Attorney’s decision not to pursue criminal charges means there was no pros-ecutorial merit to JR’s claim. The decision not to pursue criminal charges,12 made months after the actual arrest and with information not available at the time of the arrest, see Driebel, 298 F.3d at 643, does not constrain or guide our analysis of whether probable cause existed at the time Anderer was arrested. See id. (“An officer’s belief in the existence of probable cause ‘need not be based on evidence sufficient to support a conviction, nor even a showing that the officer’s belief is more likely true than false.”’) (quoting Woods, 234 F.3d at 996) (emphasis in original). It is similarly not relevant to our analysis that the booking judge commented, when ordering Anderer’s release without bail, that JR’s “allegations against [Anderer] were baseless and that the show up report presented no probable cause to have [An-derer] arrested in the first place.”
B. Retaliation for First Amendment Speech
Anderer alleges that he was retaliated against and terminated, in violation of his First Amendment rights, in response to (1) statements made by union president Bradley DeBraska, with Anderer’s apparent authorization,13 that Anderer had been arrested without probable cause as a result of IAD vindictiveness due to personal animus with one of the IAD investigators, and that the union was “hoping and praying” that he would sue the police department to correct these wrongs, (2) Anderer’s confirmation that he had retained a lawyer to look into the matter, and (3) his filing of this lawsuit against defendants.
Whether a government employee’s speech is protected by the First Amendment is a legal question that we review de novo. Gustafson v. Jones, 290 F.3d 895, 906 (7th Cir.2002). As we explained in Gustafson, there are four elements to a First Amendment retaliation claim,14 but the only element at issue here *1053is whether Anderer’s speech was a “matter of public concern.” Id. at 906-07. “Whether a government employee’s speech addresses a matter of public concern depends upon ‘the content, form, and context of [the speech] as revealed by the whole record.’ ” Id. at 907 (quoting Connick v. Myers, 461 U.S. 138, 147-48, 103 S.Ct. 1684, 75 L.Ed.2d 708 (1983)). “Of these three factors, content is the most important.” Id. (citations omitted); Campbell v. Towse, 99 F.3d 820, 827 (7th Cir.1996). “The ‘public concern’ element is satisfied if the speech can fairly be said to relate to a matter of political, social, or other concern to the community, rather than merely a personal grievance of interest only to the employee.” Gustafson, 290 F.3d at 907 (citing Connick, 461 U.S. at 146, 103 S.Ct. 1684). If the speech is not on a matter of public concern, “it is unnecessary for us to scrutinize the reasons for [the employee’s] discharge.” Connick, 461 U.S. at 146, 103 S.Ct. 1684.
The content of the speech at issue here was, quite, plainly, a matter solely of Anderer’s private concern. The speech concerned and addressed only Anderer’s arrest; nothing in these statement alleges any greater societal impact than Anderer’s possible grievance for being arrested, Connick, 461 U.S. at 147-48, 103 S.Ct. 1684; Gustafson, 290 F.3d at 908. Anderer claims that his speech was a matter of public concern because “pervasive and systematic misconduct” in the Milwaukee police department leads to a high number of arrests of officers without probable cause and that bringing this to light was the motivation for the speech. We acknowledge that motive is relevant to the “matter of public concern inquiry, [though] it is not dispositive,” Gustafson, 290 F.3d at 908 (citations omitted), but “speech on a subject that would be of interest to the public will not be protected if ‘the expression addresses only the personal effect upon the employee.” Id. (quoting Marshall v. Porter County Plan Comm’n, 32 F.3d 1215, 1219 (7th Cir.1994)). And while we recognize that there are few matters “of greater public concern in a large metropolitan area than police protection and public safety,” Auriemma v. Rice, 910 F.2d 1449, 1460 (7th Cir.1990) (en banc), nothing in the speech at issue here addresses or seeks to resolve anything about what Anderer may or may not have believed regarding the police department’s or Chief Jones’s policies, other than his dissatisfaction with his arrest and his desire for personal redress. As such, his speech cannot fairly be described as a “matter of public concern,” and any further inquiry into why he was terminated is unnecessary given the wide latitude we afford government officials in managing their offices. See Connick, 461 U.S. at 146, 103 S.Ct. 1684; Driebel, 298 F.3d at 638 (discussing internal affairs investigatory tactics employed by the Milwaukee police department).
III. CONCLUSION
For the foregoing reasons, the judgment of the district court is Affirmed.
. Because "[t]he existence of probable cause turns on the information known to the officers at the moment the arrest is made, not on subsequently-received information,” Spiegel v. Cortese, 196 F.3d 717, 723 (7th Cir.2000), we limit our recitation of facts to those known at the time of the arrest.
. Photographs were later taken that showed cuts on the inside of both of JR's lips, and blood on his shirt and pants.
. While Anderer’s question was meant to be "off the record,” Anderer put the contents of this "off the record” conversation in both his affidavit and his briefs.
. Getting "Driebel ed” is a slang term used by Milwaukee police officers that refers to a police officer who is arrested without probable cause. We assume the term takes its name from the facts underlying this court's decision in Driebel v. City of Milwaukee, 298 F.3d 622 (7th Cir.2002), in which we concluded that probable cause to arrest did in fact exist at • the time that Officer Robert J. Driebel was arrested. Id. at 645. In that case, however, we did find that there was no probable cause to arrest another officer (Officer Johnny C. Sgrignuoli). Id. at 651.
. The district court, in granting defendants' motion for a protective order, stayed all discovery pending the court’s resolution of defendants' summary judgment motion. The district court also denied Anderer’s request for copies and use of JR’s post-arrest medical records in defendants' possession (apparently unlawfully obtained). Because JR’s medical records were obtained after Anderer was arrested, they are irrelevant to the probable cause determination. See Spiegel, 196 F.3d at 723. Therefore, we do not find that the district court abused its discretion in denying Anderer’s request for access to and use of the records.
. The dissent’s analysis stresses that the summary judgment standard requires us to view all facts in the light most favorable to Anderer. While we certainly view all facts in the light most favorable to Anderer and draw all reasonable inferences in his favor, Woods, 234 F.3d at 986, our review of a probable cause determination does not ask whether an officer’s belief in the existence of probable cause is more likely true than not true. Driebel, 298 F.3d at 643. Rather, our review focuses on whether.a reasonable officer would have believed that probable cause existed to arrest Anderer based on the facts and circumstances known to the officer at the time of the arrest. See id.; see also Beauchamp v. City of Noblesville, 320 F.3d.733, 743 (7th Cir.2003).(‘‘Probable cause is only a probability or substantial chance of criminal activity, -not a certainty that a crime was committed”) (citing Illinois v. Gates, 462 U.S. 213, 244 n. 13, 103 S.Ct. 2317, 76 L.Ed.2d 527 (1983)).
. Anderer claims that JR’s story is inconsistent because while all the officers reported that JR said Anderer "hit” him in the face (statements or reports of Officers Cook and Logan, Lt. Stack, and Sgt. Jones), Anderer says one officer told him that JR had said Anderer "punched” him in the face (Del. Harrison's statement to Anderer in "off the record" conversation), and one report indicates JR said Anderer "back-handed” him in the nose and mouth (Det. Smith's report of JR’s statement to Deputy District Attorney the day after Anderer was arrested). We think this is a difference without a distinction, as they are all forms of "hits.” Furthermore, because the “back-handed” description was not known at the time of Anderer’s arrest, it is irrelevant to our analysis. See Spiegel, 196 F.3d at 723.
. Although the dissent contends that any reference to Anderer's failure to explain JR’s bloody appearance in the probable cause analysis impinges on Anderer’s Fifth Amendment and contractual rights, Anderer himself makes no such argument and, in fact, concedes his inability to explain JR’s injuries. See PL’s Resp. to Def.'s Motion for Summ. J. at 73 ("[D]efendants state they are entitled to summary judgment because it is undisputed that Anderer did not explain how J.R. was injured, or claim that he used lawful force to maintain custody of J.R. In this respect, plaintiff does not dispute these facts.”). Recall, too, that before Anderer said he did not wish to make a formal statement without union representation—the focus of the dissent's argument on this point—Anderer made several voluntary comments to other officers, including that he did not know how JR received the bloody nose. (Compl. ¶ 34; Anderer Aff. ¶¶ 60, 75, 79-81.)
. As we have noted, "[t]he existence of probable cause turns on the information known to the officers at the moment the arrest is made, not on subsequently-received information.” Spiegel, 196 F.3d at 723. In addition to later-acquired knowledge about JR's medical history, we are puzzled by the dissent's discussion of irrelevant facts which have no bearing on *1051what the officers reasonably knew when they arrested Anderer, such as: (1) the Deputy District Attorney's later decision not to pursue criminal charges; (2) subsequent investigations into Anderer’s arrest; (3) statements in affidavits signed after Anderer’s arrest containing information other than that made known to officers before Anderer’s arrest; (4) photographs of JR, as they were developed after Anderer’s arrest; and (5) statements made by identification technicians after the arrest. While the dissent’s discussion of these facts and the adequacy of the department's investigation might present a persuasive closing argument in a criminal trial, the officers did not need to establish Anderer’s guilt of the underlying charge beyond a reasonable doubt, or even by a preponderance of the evidence, before arresting him. See United States v. Funches, 327 F.3d 582, 587 (7th Cir.2003). Moreover, although the dissent emphasizes that no officer saw Anderer hit JR, that no officer saw the action does not negate the undisputed facts that a 12-year-old boy, uninjured at the time he was turned over to An-derer, arrived at a police station with blood on his face and shirt after being in Anderer’s sole control, identified Anderer as the cause of his injuries, and neither Anderer nor any other officer could offer any explanation for the boy's injuries.
. Indeed, the statement given by Officer Cook, had it been given prior to Anderer’s arrest, seems likely to have further supported the investigating officers’ determination that probable cause existed to arrest Anderer. (He told the investigators that when Anderer and JR arrived at the station, he “immediately noticed [JR] with blood running down both nostrils, his chin, blood on his shirt and both pant legs,” and "was taken aback because the kid was in perfectly good shape before he went into the squad, but not when he came out and thought that’s not good.”)
. We note that the ID techs' “observations” were not included in the initial affidavits that they provided six months after the incident, and were only included in the affidavits they *1052provided a year after they took the photographs. We review probable cause determinations based on the information available at the time of the arrest, to assess whether the arresting officer " 'acted reasonably under settled law in the circumstances, not whether another reasonable, or more reasonable, interpretation of the events can be constructed several years after the fact.' " Spiegel, 196 F.3d at 723 (quoting Humphrey, 148 F.3d at 725) (emphasis added). Similarly, the dissent’s conjecture that other factors could have caused JR's bloody nose and cuts to his face does not bear on our analysis. Again, we emphasize that our inquiry focuses on whether probable cause existed to arrest Anderer, not on whether other explanations for JR's injuries are also possible. See id.; Driebel, 298 F.3d at 643.
. The Deputy District Attorney, in his memo explaining his decision not to pursue charges, recounted the facts of JR’s claims and wrote that, while he could not "state with assurance what happened[,][he] believe[d] it more probable, particularly in view of [his] knowledge of prior complaints against Anderer, that An-derer did strike [JR]. It is entirely conceivable, however, that given [JR’s] agitation, mental problems and stated intentions to get money out of this incident, that he inflicted the injuries to himself. Such speculation, however, is not the stuff of criminal charges, and none can be proven in this case.”
. We will assume, without deciding, that speech authorized by one person but made by another could be the basis for an First Amendment claim.
. To prove a First Amendment retaliation claim in the employment context, "[f]irst, the plaintiffs must prove that their speech was a matter of public concern. Next, they must prove that their speech played at least a substantial part in the employer's decision to take an adverse employment action against them. If the plaintiffs can carry their burden on these two elements, the defendants can only prevail if they prove by a preponderance of *1053the evidence that the government’s interest, as an employer, in efficiently providing government services outweighs the employees' First Amendment interests, or if they can prove that they would have disciplined the employees even in the absence of the speech.” Id. (citing Klunk v. County of St. Joseph, 170 F.3d 772, 775 (7th Cir.1999); Hellstrom v. United States Dep’t of Veterans Affairs, 201--F.3d 94, 97 (2d Cir.2000)).