Probable Cause, Personal Involvement, and Amendment Limits in § 1983 Litigation: Commentary on Islam v. Tirelli

I. Introduction

This commentary examines the Second Circuit’s summary order in Islam v. Tirelli, No. 24‑2981‑cv (2d Cir. Nov. 24, 2025), affirming summary judgment against a plaintiff who brought a federal civil rights action under 42 U.S.C. § 1983 and related state-law claims. While the order is expressly nonprecedential under the Second Circuit’s local rules, it provides a useful synthesis of several recurring doctrines in § 1983 litigation:

When victim and eyewitness reports supply probable cause despite conflicting details;
How probable cause operates as a complete defense to false arrest and malicious prosecution claims;
The strict requirement of personal involvement for First Amendment (and other § 1983) claims; and
The limits on late efforts to substitute a named officer for a “John Doe” defendant after discovery closes.

The case arises from an incident outside a Dunkin’ Donuts in Queens, New York, where multiple witnesses, including the plaintiff’s teenage daughter, reported a physical altercation and alleged threats by the plaintiff. The plaintiff, S.M.N. Islam (“Islam”), sued Officer Andrew Tirelli, Sergeant Christian Rodriguez, the City of New York, and unnamed “John Doe” officers, asserting:

A Fourth Amendment false arrest claim;
A Fourth Amendment malicious prosecution claim;
A First Amendment free exercise claim based on an alleged denial of religiously mandated pre-prayer cleansing at a hospital; and
A state negligence claim against unknown officers who allegedly failed to detain a man who had hurt his daughter.

The district court (Cogan, J., E.D.N.Y.) granted summary judgment on all federal claims and declined to exercise supplemental jurisdiction over the remaining state negligence claim. The Second Circuit affirmed in all respects.

II. Summary of the Opinion

The Second Circuit panel (Judges Walker, Carney, and Nardini) reached the following conclusions:

False arrest: The officers had probable cause to arrest Islam for endangering the welfare of a child (N.Y. Penal Law § 260.10(1)) and harassment in the second degree (N.Y. Penal Law § 240.26(1)). Probable cause is a complete defense to false arrest, so the claim failed as a matter of law.
Malicious prosecution: Because probable cause existed to prosecute Islam for both charged offenses, the malicious prosecution claim also failed. Probable cause defeats a § 1983 malicious prosecution claim.
First Amendment (religious exercise) claim: There was no evidence that either Officer Tirelli or Sergeant Rodriguez was personally involved in the alleged denial of religious rights at the hospital. Islam himself attributed the alleged violation to an “Officer Morrish.” Absent personal involvement, the officers could not be liable under § 1983.
Leave to amend / substitute John Doe with Officer Morrish: The district court did not abuse its discretion by denying Islam’s late and procedurally improper attempt, at the summary judgment stage and after discovery had closed, to substitute “Officer Morrish” for a John Doe defendant.
State-law negligence claim: After properly disposing of all federal claims, the district court acted within its discretion in declining to exercise supplemental jurisdiction over the remaining state negligence claim.

The appellate court reviewed the grant of summary judgment de novo, found no genuine dispute of material fact, and held the defendants were entitled to judgment as a matter of law on all federal claims.

III. Detailed Analysis

A. Procedural Posture and Standard of Review

Islam commenced the action through counsel in the Eastern District of New York. After discovery, the defendants moved for summary judgment on all claims. The district court granted the motion as to all federal claims and declined supplemental jurisdiction over the remaining state negligence claim, as reflected in Islam v. Tirelli, No. 22‑cv‑812, 2024 WL 4467188 (E.D.N.Y. Oct. 10, 2024).

On appeal, Islam proceeded pro se. The Second Circuit reiterated the standard of review for summary judgment, quoting Alberty v. Hunter, 144 F.4th 408, 414 (2d Cir. 2025):

“This Court reviews a district court's grant of summary judgment de novo. Summary judgment is proper only when, construing the evidence in the light most favorable to the non-movant, there is no genuine dispute as to any material fact and the movant is entitled to judgment as a matter of law.”

The appellate court agreed that, even viewing the evidence in the light most favorable to Islam, no reasonable jury could find in his favor on the federal claims.

B. The False Arrest Claim and Probable Cause

1. Legal framework for false arrest under § 1983 and New York law

The court emphasized that, for § 1983 false arrest claims, courts generally borrow state-law elements:

“Courts should generally look to the law of the state in which the arrest occurred to determine the elements of a § 1983 claim for false arrest.” (quoting Alberty and citing Carruthers v. Colton, 153 F.4th 169, 179 (2d Cir. 2025)).

Under New York law, as summarized in Carruthers, a plaintiff must show:

The defendant intended to confine the plaintiff;
The plaintiff was conscious of the confinement;
The plaintiff did not consent to the confinement; and
The confinement was not otherwise privileged.

The critical issue here is privilege. An arrest supported by probable cause is privileged, and that ends the false arrest inquiry:

“Under both federal and New York state law, probable cause is a complete defense to a false arrest claim.” (Carruthers, 153 F.4th at 179)

2. Definition of probable cause and reliance on witness statements

The court drew on Betts v. Shearman, 751 F.3d 78 (2d Cir. 2014), to define probable cause:

“Probable cause exists when one has knowledge of, or reasonably trustworthy information as to, facts and circumstances that are sufficient to warrant a person of reasonable caution in the belief that an offense has been or is being committed by the person to be arrested.”

The panel also reaffirmed a long-standing principle: police may rely on a victim’s or eyewitness’s account to establish probable cause, unless there are clear reasons to doubt that person’s truthfulness:

When law enforcement has “received information from some person, normally the putative victim or eyewitness,” this may establish probable cause, “unless the circumstances raise doubt as to the person's veracity.” (Betts, 751 F.3d at 82)

3. Application to Islam’s arrest outside Dunkin’ Donuts

The Second Circuit agreed with the district court that the officers had probable cause to believe Islam had committed at least two offenses:

Endangering the welfare of a child (N.Y. Penal Law § 260.10(1)), which criminalizes “knowingly act[ing] in a manner likely to be injurious to the physical, mental or moral welfare of a child less than seventeen years old.”
Harassment in the second degree (N.Y. Penal Law § 240.26(1)), which applies when, “with intent to harass, annoy or alarm another person,” the offender “strikes, shoves, kicks or otherwise subjects such other person to physical contact, or attempts or threatens to do the same.”

The “undisputed evidence” on which the court relied included:

Multiple bystanders reported to police that Islam was involved in a physical altercation with his teenage daughter and had threatened to harm her.
Islam’s daughter herself told police that he had choked her and dragged her by her clothes.

These accounts, taken together, gave officers reasonably trustworthy information that Islam had:

Engaged in physical conduct that could injure his minor daughter (supporting child endangerment); and
Struck, dragged, or otherwise subjected her to unwanted physical contact or threats (supporting harassment).

4. Conflicting or incomplete information and the limits of police investigation duties

Islam argued that there were reasons to doubt the witnesses:

His daughter allegedly “changed her story multiple times”;
She did not display visible marks consistent with choking or dragging; and
Islam had previously reported her missing, which might have cast the situation in a different light.

The panel rejected these arguments, emphasizing that officers frequently operate amid conflicting or incomplete information and are not required to disprove every possible claim of innocence before acting. The court invoked two key precedents:

Ricciuti v. N.Y.C. Transit Auth., 124 F.3d 123 (2d Cir. 1997): once officers have a reasonable basis for believing there is probable cause, they are not required “to explore and eliminate every theoretically plausible claim of innocence before making an arrest.”
Bernard v. United States, 25 F.3d 98 (2d Cir. 1994): probable cause can rest on mistaken or incorrect information so long as the officer reasonably and in good faith relied on it.

The panel applied those principles to hold:

“Here, the statements made by Islam's daughter and various bystanders were not fatally undermined by the counterpoints that Islam identifies, and so we cannot say that the officers in this case failed to act reasonably or in good faith when arresting him based on the information they had received.”

Accordingly, the alleged inconsistencies, lack of visible injuries, or background context about a prior missing person report did not negate probable cause. At most, they created conflicting versions of events that officers were not legally obliged to resolve before effectuating the arrest.

Because probable cause existed as a matter of law, the confinement was “privileged,” and the false arrest claim failed.

C. Malicious Prosecution and Charge-by-Charge Probable Cause

1. Elements of § 1983 malicious prosecution

The Second Circuit turned next to Islam’s malicious prosecution claim and adopted, via Carruthers, the familiar five-part test:

The commencement or continuation of a criminal proceeding by the defendant against the plaintiff;
Termination of the proceeding in favor of the accused;
Absence of probable cause for the criminal proceeding;
Actual malice; and
A sufficient post-arraignment liberty restraint to implicate the plaintiff’s Fourth Amendment rights.

As with false arrest, the court stressed:

“Probable cause is a complete defense to a constitutional claim of malicious prosecution.”

However, the conception of probable cause differs slightly in this context:

“Probable cause, in the context of malicious prosecution, has been described as such facts and circumstances as would lead a reasonably prudent person to believe the plaintiff guilty.”

Critically, the court emphasized a “charge-by-charge” approach:

“In assessing probable cause for a malicious prosecution claim, in contrast to a false arrest claim, courts must evaluate suits charge by charge. That is, probable cause must be shown as to each crime charged in the underlying criminal action.”

2. Application to the charges against Islam

Islam was ultimately charged with:

Endangering the welfare of a child (N.Y. Penal Law § 260.10(1)); and
Harassment in the second degree (N.Y. Penal Law § 240.26(1)).

The Second Circuit had already identified facts sufficient to establish probable cause that Islam committed each of these offenses. Therefore, when the malicious prosecution claim is assessed “charge by charge,” probable cause exists as to both counts.

Because the “absence of probable cause” is a required element of malicious prosecution, the claim necessarily failed. Having found probable cause, the court did not need to reach the issues of:

Whether the criminal case terminated in Islam’s favor in a way that satisfies current Second Circuit standards; or
Whether there was “actual malice” on the part of the officers or prosecutors.

Thus, as in many § 1983 malicious prosecution cases, the probable cause determination was dispositive.

D. First Amendment Free Exercise Claim and Personal Involvement

1. Personal involvement requirement under § 1983

Islam claimed that after his arrest he was taken to a hospital due to chest pain, placed in leg restraints, and, as a result, could not perform the pre-prayer washing of his feet required by his religious beliefs. He alleged that this interference with ritual cleansing violated his First Amendment right to free exercise of religion.

The Second Circuit did not reach the substantive First Amendment question, because a threshold requirement of any § 1983 claim is that each defendant must be personally involved in the alleged constitutional violation. Relying on Wiggins v. Griffin, 86 F.4th 987 (2d Cir. 2023), the court stated:

“To establish a Section 1983 violation, a plaintiff must plead (and later prove) that each defendant was personally involved in the alleged constitutional violation.”

This rule means:

There is no vicarious liability or “respondeat superior” under § 1983 for line officers or supervisors solely because of their rank.
Each named defendant must have directly participated in, ordered, or otherwise been causally connected to the challenged conduct.

2. No evidence that Tirelli or Rodriguez participated in the alleged violation

The evidentiary record showed that:

Islam was taken to the hospital and placed in leg restraints to prevent his escape; and
He asserted that an “Officer Morrish” denied him the ability to pray in accordance with his religious practices.

Crucially, Islam did not identify Officer Andrew Tirelli or Sergeant Christian Rodriguez as the officers who restrained him at the hospital or interfered with his prayer. Instead, he consistently named Officer Morrish as the actor responsible for the alleged First Amendment violation.

Because there was no evidence that Tirelli or Rodriguez:

Were present at the hospital during the relevant time;
Ordered or directed the use of leg restraints at the hospital; or
Otherwise participated in or were aware of the alleged denial of religious accommodations,

the panel held that they could not be held liable under § 1983 for this claim. Summary judgment was therefore appropriate.

3. The attempted late substitution of Officer Morrish for a John Doe defendant

Anticipating the problem of personal involvement, Islam attempted—only in his opposition to summary judgment— to “substitute” Officer Morrish for one of the “John Doe” officers named in his original complaint. The district court rejected this attempt, and the Second Circuit affirmed.

The panel noted:

Islam was represented by counsel throughout the district court proceedings (only later proceeding pro se on appeal).
Despite this, he never filed a formal motion to amend the complaint to add or substitute Officer Morrish.
Discovery had already closed, and the case was at the summary judgment stage when he raised the issue in his opposition papers.

Under Federal Rule of Civil Procedure 15(a), courts should “freely give leave [to amend] when justice so requires.” However, as the Second Circuit reiterated (citing Zahra v. Town of Southold, 48 F.3d 674 (2d Cir. 1995)), grant or denial of leave to amend is within the district court’s “sound discretion.” Leave may be denied when there is:

Futility of the amendment;
Bad faith;
Undue delay; or
Undue prejudice to the opposing party.

The panel relied on TechnoMarine SA v. Giftports, Inc., 758 F.3d 493 (2d Cir. 2014), which confirms these grounds for denying leave to amend even under the otherwise liberal Rule 15 standard.

Here, the Second Circuit found no abuse of discretion. Key factors:

No proper Rule 15 motion was made at all;
The request came late—only after discovery was completed and while summary judgment was pending; and
Granting the request could have prejudiced defendants and delayed resolution of the case (for example, by reopening discovery to explore claims against a new individual defendant).

Islam’s failure to timely and properly amend his complaint thus prevented the court from considering his First Amendment claim against the officer he alleged was responsible.

E. Supplemental Jurisdiction Over State-Law Negligence Claim

Islam’s final claim was a state-law negligence claim against unnamed officers who allegedly failed to detain a man who had hurt his daughter. After dismissing all federal claims, the district court declined to exercise supplemental jurisdiction over this state-law negligence claim.

Although the Second Circuit’s summary order does not cite the federal supplemental jurisdiction statute by number, the governing framework is 28 U.S.C. § 1367. Under § 1367(c), a district court may decline supplemental jurisdiction when:

The claim raises novel or complex state-law issues;
The state claim substantially predominates over the federal claims;
All federal claims have been dismissed; or
In exceptional circumstances, there are other compelling reasons for declining jurisdiction.

Once the federal claims were disposed of at summary judgment, the court was squarely within the third category: all claims over which it had original jurisdiction had been dismissed. The Second Circuit saw no abuse of discretion in allowing the remaining purely state-law negligence claim to proceed, if at all, in state court rather than federal court.

F. Role of the Precedents Cited

The opinion relies on several prior Second Circuit decisions to structure its analysis:

Alberty v. Hunter, 144 F.4th 408 (2d Cir. 2025):
Cited for the standard of review: grants of summary judgment are reviewed de novo, and summary judgment is appropriate only if no genuine dispute of material fact exists, viewing the evidence in the light most favorable to the non-moving party.
Carruthers v. Colton, 153 F.4th 169 (2d Cir. 2025):
Supplies the elements of New York false arrest and malicious prosecution claims and reiterates that probable cause is a complete defense to both. It also clarifies the need to analyze probable cause “charge by charge” in malicious prosecution actions.
Betts v. Shearman, 751 F.3d 78 (2d Cir. 2014):
Defines probable cause and emphasizes that reliable victim or eyewitness reports can alone support probable cause, absent serious reasons to doubt the witness’s veracity.
Ricciuti v. N.Y.C. Transit Auth., 124 F.3d 123 (2d Cir. 1997):
Clarifies that officers are not required to exhaust all possible exculpatory leads or “explore and eliminate every theoretically plausible claim of innocence” once they have a reasonable basis for probable cause.
Bernard v. United States, 25 F.3d 98 (2d Cir. 1994):
States that probable cause can be founded on mistaken or incomplete information, provided officers reasonably and in good faith rely on the information at hand.
Wiggins v. Griffin, 86 F.4th 987 (2d Cir. 2023):
Asserts the non-negotiable requirement of personal involvement in § 1983 claims: each defendant must be personally connected to the alleged violation; mere supervisory status or chain-of-command placement does not suffice.
Zahra v. Town of Southold, 48 F.3d 674 (2d Cir. 1995):
Affirms that granting or denying leave to amend under Rule 15(a) is within the district court’s sound discretion.
TechnoMarine SA v. Giftports, Inc., 758 F.3d 493 (2d Cir. 2014):
Explains that leave to amend may be denied for “good reason,” including futility, bad faith, undue delay, or undue prejudice to the opposing party—standards used to uphold the denial of Islam’s late amendment effort.

These cases collectively formed a straightforward doctrinal framework that left little room for Islam to survive summary judgment once the court credited the undisputed witness accounts and applied the personal involvement requirement.

G. Simplifying Key Legal Concepts

The opinion invokes several doctrines that often cause confusion. In plain terms:

1. Summary judgment

Summary judgment is a procedure for resolving a case without trial when there is no real dispute about the facts that matter, and the moving party is entitled to win under the law. The court must:

View the evidence in the light most favorable to the non-moving party (here, Islam); and
Determine whether any reasonable jury could find for that party on the essential elements of the claim.

If not, the court grants judgment as a matter of law to the opposing side.

2. Probable cause

Probable cause is a practical, non-technical standard. It asks: based on the facts and reasonably trustworthy information available to the officer at the time, would a person of “reasonable caution” believe that a crime has been, or is being, committed by the suspect?

It does not require proof beyond a reasonable doubt (the criminal trial standard);
It does not require that the officer be correct in hindsight; and
It allows reliance on victim or eyewitness statements unless there is a clear reason to distrust them (e.g., obvious bias, internal contradictions that make the story implausible on its face, etc.).

3. False arrest vs. malicious prosecution

False arrest focuses on the initial seizure—whether the decision to arrest was justified by probable cause at the time the person was taken into custody.
Malicious prosecution arises when, after an arrest, criminal charges are pursued for improper reasons and without probable cause, resulting in an unjustified criminal proceeding.

Both require “absence of probable cause” as a key element; thus, probable cause is often the central battleground.

4. Personal involvement in § 1983 claims

Section 1983 provides a cause of action against any “person” who, under color of state law, violates federal rights. But a plaintiff must show that:

The specific individual defendant participated in or directly caused the violation; and
Liability cannot be imposed merely because the person was a supervisor or because some other officer violated the Constitution.

The Wiggins case reinforces that this requirement is strict and must be supported by evidence, not just general allegations.

5. John Doe defendants and amendment of pleadings

Plaintiffs sometimes name “John Doe” defendants when they do not yet know specific officers’ identities. To actually pursue claims against those individuals, plaintiffs must:

Identify the individuals (through discovery or otherwise) within the limitations period; and
Formally move to amend the complaint under Rule 15(a) to substitute the real names for the Doe placeholders.

Courts may deny late amendments, especially when:

The plaintiff unduly delayed seeking amendment;
Discovery is already closed;
The case is at or near summary judgment; and
The amendment would prejudice the defense (e.g., by requiring new discovery or trial delays).

In Islam v. Tirelli, Islam’s failure to follow these steps in a timely and proper manner was fatal to his attempt to pursue claims against Officer Morrish.

6. Supplemental jurisdiction

When a plaintiff brings both federal and state claims in federal court, the federal court can usually hear the state claims under “supplemental jurisdiction.” But if all federal claims are dismissed before trial, courts often choose (and are permitted) to dismiss the state claims without prejudice so they may be pursued in state court instead, if the plaintiff wishes.

H. Practical and Doctrinal Impact

Although this is a summary order without precedential effect under Federal Rule of Appellate Procedure 32.1 and the Second Circuit’s Local Rule 32.1.1, it still provides practical guidance to litigants and lower courts.

1. For civil rights plaintiffs and their counsel

Challenging probable cause is difficult when multiple witnesses corroborate the offense.
Where multiple bystanders and the alleged victim independently report conduct that clearly falls within statutory definitions (here, child endangerment and harassment), arguing that officers should have doubted those accounts is an uphill battle. Minor inconsistencies, absence of visible injuries, or background context are usually insufficient to defeat probable cause at summary judgment.
Develop concrete evidence of witness unreliability.
To challenge probable cause based on victim or eyewitness accounts, plaintiffs need specific, compelling evidence that those witnesses were not credible (e.g., clear contradictions, documented motives to fabricate, or prior recantations) that would have been apparent to a reasonable officer at the time.
Establish personal involvement with precision.
Name the correct officers in connection with the specific alleged violation (e.g., who applied restraints, who gave orders, who denied a religious accommodation) and build the evidentiary record around those individuals. Vague references to “officers” are not enough.
Act promptly to identify and substitute John Doe defendants.
Counsel must use discovery to identify Doe defendants early, then file a proper Rule 15 motion to amend before discovery closes and before the summary judgment stage, explaining why the amendment is timely and will not prejudice defendants.
Do not rely on informal amendment requests in summary judgment briefing.
Asking the court in opposition papers to “substitute” a new defendant is not a substitute for a timely, formal motion to amend the complaint.

2. For law enforcement and municipalities

Reaffirmation of reliance on victim and eyewitness reports.
The order confirms that officers may reasonably act on statements from the alleged victim and multiple witnesses to establish probable cause, even if the scene is chaotic or if information is not perfectly consistent.
Domestic and family-related incidents.
The case specifically involves alleged violence by a parent against a teenager. The panel’s analysis underscores that officers have substantial leeway to intervene quickly in suspected child endangerment scenarios based on on-the-scene reports.
Importance of documenting who does what.
For municipalities, clear documentation (body cameras, incident reports, hospital custody logs) showing which officers were involved in each phase of custody (on-scene arrest vs. hospital escort) can be decisive in defeating personal involvement allegations at summary judgment.

3. For the development of § 1983 doctrine

Continuity, not novelty.
The order does not announce new doctrinal standards. Instead, it illustrates the steady application of longstanding principles: probable cause as a complete defense; personal involvement as a necessary element; the discretion to deny late amendments; and the routine practice of relinquishing supplemental jurisdiction over state claims when all federal claims are gone.
Persuasive value.
While nonprecedential, the order may be cited and can have persuasive force, particularly where facts are similar (e.g., conflicting accounts in a parent-child altercation, religious exercise claims tied to specific actions of discrete officers, or belated efforts to add Doe defendants).

IV. Conclusion

Islam v. Tirelli underscores how established doctrines in § 1983 litigation operate in practice. The Second Circuit’s summary order affirms that:

Probable cause founded on victim and eyewitness statements—even amid some inconsistencies—defeats both false arrest and malicious prosecution claims;
Malicious prosecution must be analyzed charge by charge, but probable cause as to each charge ends the claim;
Each § 1983 defendant must be personally involved in the alleged constitutional violation; naming the wrong officer or failing to timely amend to add the right one can be fatal to the claim; and
District courts retain broad discretion to deny late amendments and to decline supplemental jurisdiction over state-law claims once all federal claims are dismissed.

Although it is formally nonprecedential, the opinion offers a clear, practical illustration of how federal courts scrutinize claims at the summary judgment stage in § 1983 actions, and it serves as a cautionary example about the evidentiary and procedural rigor such cases demand.