Tenth Circuit Tightens Pleading and Causation Requirements for § 1983 Malicious Prosecution Based on Affidavit Defects and Requires Post-Disposition Reassessment of Supplemental Jurisdiction

1. Introduction

Horocofsky v. City of Lawrence, Kansas (10th Cir. Sept. 10, 2026) arises from a sexual-assault report made by Plaintiff Bobbie Jo Horocofsky, a University of Kansas law student. She alleged a classmate, Joel Thompson, raped her. The investigation pivoted: Lawrence Police Department officers investigated her for false reporting, and she was charged with multiple counts of making false accusations. After the charges were dismissed with prejudice, she sued LPD Officers Charles Cottengim and Kimberlee Nicholson (and the City) under federal civil-rights statutes and Kansas law.

The appeal presented four principal issues: (1) whether the First Amended Complaint plausibly stated federal claims for malicious prosecution and conspiracy against the officers; (2) whether the district court properly denied late leave to add a Fourth Amendment phone-search claim; (3) whether summary judgment was proper on an Equal Protection claim alleging gender-biased policing; and (4) what to do with state-law claims once all federal claims are resolved before trial.

Procedurally, the court also denied a petition for rehearing en banc and issued a revised opinion with only non-substantive changes.

2. Summary of the Opinion

  • Malicious prosecution (§ 1983): Affirmed dismissal for failure to plead causation. The court held the complaint did not plausibly allege that the officers “caused” the prosecution—particularly because the theory depended on defects in Officer Cottengim’s probable-cause affidavit, and the alleged misstatements/omissions were not pleaded as knowingly/recklessly false and/or were not material to probable cause.
  • Conspiracy (§§ 1983 and 1985(3)): Affirmed dismissal. Allegations showed, at most, coordinated investigation (lawful activity), not a pleaded “meeting of the minds” to violate rights, and relied too heavily on conclusory and collective assertions.
  • Late amendment (Fourth Amendment phone search): Affirmed denial under Rule 16(b)(4). Even assuming plaintiff first learned key facts in July 2023 depositions, she did not show diligence/good cause for waiting roughly five months after notice to seek amendment.
  • Equal Protection (§ 1983): Affirmed summary judgment. Plaintiff failed to identify a similarly situated comparator (e.g., Thompson) “alike in all relevant respects,” and the offered circumstantial evidence did not support an inference of gender discrimination by these defendants.
  • State-law claims: Reversed and remanded. After all federal claims were resolved before trial, the district court ordinarily should consider declining supplemental jurisdiction under 28 U.S.C. § 1367(c)(3); the record did not show it performed that post-disposition analysis.

3. Analysis

3.1. Precedents Cited

A. Pleading standards, documents considered on a motion to dismiss

  • Bledsoe v. Carreno: Reiterated the two-step approach at Rule 12(b)(6): disregard conclusory allegations, then test plausibility. The court used Bledsoe to reject broad characterizations of the affidavit (“full of omissions”) not anchored in specific facts.
  • Ashcroft v. Iqbal: Provided the plausibility framework; the court applied it to require concrete, nonconclusory allegations about what was false/omitted, the officer’s mental state, and materiality.
  • GFF Corp. v. Associated Wholesale Grocers, Inc.: Allowed consideration of a referenced, authentic affidavit at the pleadings stage. This mattered because the court could rely on the actual affidavit to contradict the complaint’s characterizations.
  • Robbins v. Oklahoma: Emphasized individualized pleading in § 1983 cases—“who did what to whom”—and discouraged “collective” “Defendants” allegations. This theme recurred in rejecting conspiracy allegations and generalized “LPD” conduct.

B. § 1983 malicious prosecution causation through affidavit defects

  • Coones v. Bd. of Cnty. Comm'rs of Unified Gov't of Wyandotte Cnty./Kan. City: Supplied the five elements of a Tenth Circuit malicious-prosecution claim, particularly element (1) “defendant caused” prosecution/confinement.
  • Taylor v. Meacham and Albright v. Oliver: Framed the “anomalous” nature of malicious prosecution against police, because prosecutors/judges typically break the causal chain. The court used Taylor to underscore that a preliminary hearing finding probable cause often interrupts causation unless the officer tainted the process.
  • Pierce v. Gilchrist: Gave the pathway to causation despite the prosecutor/judge “break”: an officer can be a cause if they knowingly or recklessly include false statements or omit facts that are material enough to vitiate probable cause and thereby induce prosecution. This was the doctrinal centerpiece for rejecting plaintiff’s affidavit-based theory.
  • Kapinski v. City of Albuquerque: Clarified “recklessness” (serious doubts about truth) and, importantly here, supported an inference that including some exculpatory information can negate an inference of reckless omission.
  • United States v. Pulley (4th Cir.): Adopted for the proposition that omission liability requires actual knowledge; “should have known” is not enough if the affiant did not, in fact, know the information.
  • Franks v. Delaware: Used to distinguish “truthfulness” from “factual correctness,” focusing on whether the affiant believed/appropriately accepted the information as true. This helped the court treat the “autocorrect” argument as, at most, a mistaken inference—not a knowingly false statement about what the officer believed.
  • Shrum v. Cooke: Cited to rebut the argument that Taylor is limited to summary judgment; the causation framework applies at the motion-to-dismiss stage too.
  • Becker v. Kroll: Waiver doctrine—arguments not developed in the opening brief are waived—used to confine plaintiff to her affidavit-based causation theory on appeal.

C. Conspiracy pleading requirements

  • Dixon v. City of Lawton: Recognized § 1983 conspiracy as an agreement to deprive constitutional rights under color of law.
  • Brooks v. Gaenzle (abrogated on other grounds by Torres v. Madrid): Provided the elements of § 1985(3) conspiracy (including class-based discriminatory animus) and, crucially, the shared “meeting of the minds” requirement for § 1983 and § 1985 conspiracies.
  • Tonkovich v. Kan. Bd. of Regents: Required “more than conclusory allegations” for conspiracy.
  • Bell Atl. Corp. v. Twombly: “Parallel conduct does not suggest conspiracy” without additional factual matter suggesting agreement.
  • Frasier v. Evans and Grider v. City of Auburn (11th Cir.): Supported the key distinction that agreement to conduct lawful investigative activity—even close coordination—does not equal an agreement to violate rights (e.g., to maliciously prosecute).

D. Late amendments after scheduling-order deadlines

  • Gorsuch, Ltd., B.C. v. Wells Fargo Nat'l Bank Ass'n: Set the two-step post-deadline amendment framework: Rule 16(b)(4) good cause first, then Rule 15(a). Also emphasized diligence and that known conduct not pleaded before deadline is generally barred.
  • Birch v. Polaris Indus., Inc. and Husky Ventures, Inc. v. B55 Invs., Ltd.: Applied the diligence requirement and approved denial where parties waited months after notice without adequate explanation.
  • Fed. R. Civ. P. 16 advisory committee's note: Reinforced that “good cause” turns on inability to meet deadlines despite diligence.

E. Equal Protection: comparators and circumstantial proof

  • Corder v. Lewis Palmer Sch. Dist. No. 38: Equal Protection’s core command—similarly situated persons should be treated alike.
  • Brown v. Montoya and Ashaheed v. Currington: Required a threshold showing of different treatment of similarly situated persons “alike in all relevant respects,” and demanded specific facts about who was treated differently.
  • Watson v. City of Kansas City: Recognized no general constitutional right to police protection, but forbade discriminatory provision of police protection—invoked by plaintiff to argue gender-biased policing.
  • Fowler v. Stitt: Cited for the proposition that Equal Protection can be proven via “totality of the relevant facts,” not exclusively by a male comparator or statistics; the court nevertheless found plaintiff’s totality-of-evidence insufficient here.
  • Kendrick v. Penske Transp. Servs., Inc.: Mentioned in discussing (and deeming waived) plaintiff’s “direct evidence” argument.

F. Supplemental jurisdiction after federal claims drop out before trial

  • Barnett v. Hall, Estill, Hardwick, Gable, Golden & Nelson, P.C.: Reflected the Supreme Court’s encouragement to dismiss/remand state claims when federal claims drop out pretrial.
  • Brooks v. Gaenzle: Strongly stated district courts “should decline” supplemental jurisdiction in that circumstance, emphasizing comity/federalism.
  • Merrifield v. Bd. of Cnty. Comm'rs for Cnty. of Santa Fe and Ball v. Renner: Examples of the Tenth Circuit applying the norm of declining supplemental jurisdiction after federal claims are resolved.

3.2. Legal Reasoning

A. Malicious prosecution: causation narrowly policed when the theory is “affidavit defects”

The court treated plaintiff’s malicious-prosecution theory as turning entirely on Officer Cottengim’s probable-cause affidavit. Applying Pierce v. Gilchrist, it asked whether plaintiff plausibly alleged (i) knowing/reckless falsity or omission, (ii) materiality to probable cause, and (iii) inducement of the criminal justice system to prosecute.

Two aspects of the reasoning are especially consequential:

  • Inference vs. falsity: The affidavit stated the officer believed plaintiff and Thompson were coherent enough to type correctly spelled texts. Plaintiff countered with the “autocorrect” point. The court, using Franks v. Delaware, treated this as potentially a mistaken inference, not a knowingly false statement—because the complaint did not allege the officer misrepresented his own belief.
  • Omissions require actual knowledge and materiality: The court leaned on United States v. Pulley to reject omission theories where plaintiff did not plausibly allege the officer actually knew the omitted medical/rape-kit/drink-purchase/video evidence at the time of the affidavit. Separately, it found several alleged omissions immaterial because the affidavit already conveyed key points (e.g., intoxication) or the extra detail would not change probable cause.

This approach reinforces that a plaintiff cannot survive dismissal by characterizing an affidavit as misleading without pleading the officer’s mental state, actual knowledge of omitted facts, and a concrete explanation of how the corrected affidavit would negate probable cause.

B. Conspiracy: coordination is not agreement to violate rights

The court demanded plausible facts showing a “meeting of the minds” under Brooks v. Gaenzle, Tonkovich v. Kan. Bd. of Regents, and Twombly. It held allegations that officers worked closely with a university Title IX investigator or shared information described, at most, lawful investigative collaboration—insufficient under Frasier v. Evans and Grider v. City of Auburn.

It also applied Robbins v. Oklahoma to reject generalized assertions about “detectives” or “LPD” (including alleged celebratory “high-fives”) absent specific allegations tying these defendants to the conduct or to an unlawful agreement.

C. Rule 16 “good cause”: diligence measured from notice, not from perfected proof

On the phone-search claim, the court accepted (for argument’s sake) plaintiff’s premise that she first learned in a July 2023 deposition that the download exceeded her consent. Even so, the court focused on the diligence requirement articulated in Gorsuch, Birch, and Husky Ventures: once on notice, a party must move promptly or explain why it could not.

Plaintiff’s desire to retain experts and learn the “full scope” of the search did not constitute good cause where she failed to explain why amendment could not have been sought earlier based on the core fact (search beyond consent) already known. The opinion thus treats “good cause” as a discipline of litigation management, not an invitation to wait until evidentiary development is optimal.

D. Equal Protection: comparator requirement remains central absent strong alternative proof

Plaintiff’s primary comparator was Thompson, but the court held they were not similarly situated “in all relevant respects” under Ashaheed v. Currington: they were accused of different offenses, occupied different roles in the investigation (complainant vs. suspect), and had different patterns of consistency.

The court then considered the “totality” approach referenced in Fowler v. Stitt and the discriminatory-protection principle from Watson v. City of Kansas City. It found the offered circumstantial evidence too thin and not tied to these defendants, particularly where abrasive conduct or skepticism, without more, does not plausibly show gender discrimination.

E. Supplemental jurisdiction: a required moment of reconsideration

The most institutionally oriented part of the decision concerns state-law claims. Once the last federal claim (Equal Protection) fell on summary judgment, the case was in the posture addressed by Barnett and Brooks: federal claims dropped out before trial, so the district court ordinarily should decline supplemental jurisdiction under 28 U.S.C. § 1367(c)(3).

Because the record did not show the district court performed that post-disposition analysis, the Tenth Circuit reversed the merits disposition of the state-law claims and remanded for the district court to decide whether to retain or dismiss them.

3.3. Impact

  • For § 1983 malicious prosecution pleadings: The decision underscores that when a plaintiff tries to bridge the prosecutor/judge causation “gap” through affidavit defects, courts will require granular allegations of (i) what is false or omitted, (ii) the affiant’s knowledge/mental state, and (iii) why the corrected affidavit defeats probable cause. Assertions about what police “should have investigated” will not substitute for pleading what the affiant actually knew at the time of the affidavit.
  • For conspiracy claims: “Worked closely,” “shared information,” and other collaboration allegations will often be characterized as lawful investigative conduct unless the complaint includes nonconclusory facts supporting an agreement to commit an unlawful act.
  • For late constitutional amendments (Rule 16): Parties should treat depositions that reveal new claim predicates as starting the diligence clock. Waiting months to seek amendment while building expert support risks denial absent a concrete explanation why amendment could not be filed earlier.
  • For Equal Protection claims alleging biased policing: Comparator evidence remains the cleanest route; absent that, plaintiffs must marshal stronger circumstantial evidence tied to the defendants (patterns, statements, statistics, or clearly comparable cases) rather than general criticisms of a department’s culture.
  • For district courts handling pendant state claims: The opinion reinforces that courts should explicitly revisit supplemental jurisdiction once federal claims are resolved before trial, rather than silently proceeding to adjudicate state claims on the merits.

4. Complex Concepts Simplified

  • “Malicious prosecution” under § 1983: A civil-rights claim alleging a person was prosecuted without probable cause and with malice, causing harm. In the Tenth Circuit (per Coones v. Bd. of Cnty. Comm'rs of Unified Gov't of Wyandotte Cnty./Kan. City), the plaintiff must also show the defendant caused the prosecution.
  • “Causation” and the prosecutor/judge “break”: Because prosecutors file charges and judges may find probable cause, a police officer is not automatically responsible for the prosecution’s continuation. Under Taylor v. Meacham and Pierce v. Gilchrist, causation can reattach if the officer materially taints the process through knowing/reckless falsehoods or omissions in key warrant materials.
  • “Material” omission/misstatement: An error is “material” if correcting it would remove probable cause—i.e., the corrected affidavit would not justify the arrest/prosecution.
  • Rule 16(b)(4) “good cause”: After a scheduling deadline passes, a party must show it acted diligently and could not reasonably meet the deadline. Wanting more evidence is not, by itself, good cause if the party already knows the essential facts needed to plead the claim.
  • Equal Protection “similarly situated”: You generally must identify others who are comparable in the relevant ways but were treated better. If the comparator is different in key respects (different suspected crimes, different role in the investigation), courts will likely reject the comparison.
  • Supplemental jurisdiction: Federal courts can hear state claims related to federal claims in the same case, but when the federal claims are gone before trial, federal courts usually dismiss the state claims so state courts decide state-law issues.

5. Conclusion

Horocofsky is a pleading- and procedure-centered decision. It reinforces that § 1983 malicious prosecution claims against officers—especially those predicated on affidavit defects—require tightly pleaded facts establishing knowing/reckless falsity or omission, actual knowledge, and materiality sufficient to overcome the usual causation break created by prosecutorial charging decisions and judicial probable-cause determinations. It likewise confirms that conspiracy claims require plausible, defendant-specific allegations of agreement to violate rights—not merely parallel or coordinated investigation.

On case management, the decision illustrates the Tenth Circuit’s strict enforcement of Rule 16 diligence once a party is on notice of a potential claim. And on federalism, it emphasizes that when federal claims drop out before trial, district courts should ordinarily reconsider and likely decline supplemental jurisdiction over state-law claims.