Late-Disclosed “Grooming” Expert Testimony and Hybrid Police Witnesses: Abuse of Discretion Absent Good Cause and Safeguards (State v. Fomo)

Case: State v. Fomo (Concurrence)
Court: Supreme Court of Connecticut
Date: 2026-09-15
Opinion Type: Concurring opinion by Ecker, J. (joined by McDonald and D’Auria, Js.)

1. Introduction

In State v. Fomo (Concurrence), Justice Ecker agrees with the majority’s disposition but writes separately to address a recurring trial-management problem in Connecticut criminal practice: the admission of expert opinions without timely expert disclosure, and the heightened risk of unfair prejudice and juror confusion when an investigating police officer also testifies as an expert (a “hybrid” or “dual” witness).

The concurrence focuses on the trial court’s decision to allow the State’s investigating officer, Detective Todd McCormack, to provide expert opinion testimony defining “grooming” despite (1) the State’s failure to disclose him as an expert under the criminal discovery rules and (2) the absence of safeguards typically used when a law enforcement fact witness is also presented as an expert. Although finding the admission erroneous and an abuse of discretion, the concurrence ultimately agrees the error was harmless.

2. Summary of the Opinion

Justice Ecker identifies two independent reasons the trial court abused its discretion by admitting Detective McCormack’s expert testimony on “grooming”:

  • Discovery violation: The State did not timely disclose McCormack as an expert witness as required by Practice Book § 40-13 (a), offered no “good cause” for late disclosure, and previously represented in open court that it would present no expert testimony.
  • Hybrid-witness dangers: McCormack served both as investigating officer (fact witness) and as an expert on criminal conduct, creating risks that jurors will over-credit the testimony or be confused about which portions are fact, lay opinion, or expert opinion—risks that were not mitigated by any of the recognized procedural safeguards.

The concurrence rejects the prosecutor’s “opening the door” rationale for late expert testimony and notes a further concern: the trial court itself may have catalyzed the expert framing by asking whether the State was offering McCormack as “some type of expert witness.”

Despite these errors, Justice Ecker agrees with the majority that the admission was harmless under the standard articulated in State v. Ayala: the court must have “a fair assurance that the error did not substantially affect the verdict.”

3. Analysis

3.1 Precedents Cited

A. Timely expert disclosure; “good cause” requirement; discovery integrity

  • State v. Mallozzi: The concurrence relies on State v. Mallozzi, 355 Conn. 84, 97, 359 A.3d 125 (2026), for the proposition that when a party seeks to admit late-disclosed evidence, “it is incumbent on the [party] ... to make a showing of good cause for any late disclosure.” This frames the disclosure failure as not merely technical but as a burden the State must satisfy before the trial court may permissibly allow the evidence.
  • State v. Dabate: The concurrence echoes State v. Dabate, 351 Conn. 428, 461, 331 A.3d 1159 (2025), emphasizing that “[c]riminal discovery is not a game” and is “integral to the quest for truth and the fair adjudication of guilt or innocence.” The case is used to situate the issue as systemic and recurring, not isolated.
  • State v. Hargett and State v. Jackson: Cited as additional Connecticut examples illustrating that expert disclosure problems “appear[] to be a recurrent problem,” supporting the concurrence’s call for “greater vigilance” and potential procedural reform.

B. “Opening the door” doctrine and its limits

  • State v. Payne: The concurrence uses State v. Payne, 303 Conn. 538, 558, 34 A.3d 370 (2012), to reject the notion that routine cross-examination “open[s] the door” to otherwise inadmissible evidence. “Opening the door” is limited to preventing a party from selectively presenting evidence while blocking contextual completion by the opponent.
  • State v. Graham: Quoting State v. Graham, 200 Conn. 9, 13, 509 A.2d 493 (1986), the concurrence warns the doctrine cannot be “subverted into a rule for injection of prejudice.” This directly counters the prosecutor’s attempt to use “opening the door” as a substitute for compliance with expert-disclosure rules.

C. Hybrid/dual-role witnesses and juror confusion

  • State v. Tomlinson: The concurrence invokes State v. Tomlinson, 340 Conn. 533, 553 n.7, 264 A.3d 950 (2021), acknowledging the practical difficulty of separating fact testimony from expert testimony when witnesses rely on experience—setting the stage for why safeguards matter.
  • United States v. Cruz: The Second Circuit’s caution in United States v. Cruz, 363 F.3d 187, 194 (2d Cir. 2004), is central: dual testimony is not categorically improper, but it can confer an “aura of special reliability and trustworthiness” that requires “especially vigilant” admissibility review.
  • United States v. Williams: The concurrence relies on United States v. Williams, 827 F.3d 1134, 1160 (D.C. Cir. 2016), cert. denied sub nom. Edwards v. United States, 580 U.S. 1083, 137 S. Ct. 706, 196 L. Ed. 2d 579 (2017), for the risk that jurors must perform “mental gymnastics” to decide when the witness is expert versus fact witness, and that an expert instruction may cause the jury to treat all the witness’s opinions as “based on ... expertise.”
  • State v. Raynor: Cited for the proposition that juries give “great credence and weight” to experts, heightening prejudice when a fact witness receives expert imprimatur.
  • United States v. Moralez: Supports the practical directive that courts and counsel “should take appropriate measures” to minimize dual-role problems.

D. Safeguards endorsed by federal courts and evidence authorities

  • United States v. Vera and United States v. Lopez-Medina: Cited for using jury instructions to clarify and limit juror confusion about dual-role testimony.
  • United States v. Tucker: Cited for structuring testimony to make clear when the witness is testifying to facts versus expert opinions.
  • United States v. Christian: Cited both for foundation requirements distinguishing expert from lay opinions and for the “especially heavy burden” on courts in dual-testimony scenarios, particularly where the conduct may “appear innocent.”
  • Fed. R. Evid. 702, advisory committee notes to 2000 amendment: Cited for the caution against labeling the witness an “expert” in ways that may place the court’s “stamp of authority” on the witness’s opinions.

E. Whether “grooming” requires expert testimony

  • In re Personal Restraint of Phelps and Morris v. State are juxtaposed to show a live doctrinal divide: some courts treat “grooming” as within common juror knowledge; others treat it as beyond ordinary understanding. The concurrence expressly “express[es] no opinion” on which view should govern in Connecticut, but flags the debate.

F. Harmless error standard

  • State v. Ayala: Supplies the harmlessness test applied by the majority and accepted by the concurrence—whether there is “a fair assurance that the error did not substantially affect the verdict.”

3.2 Legal Reasoning

A. The disclosure failure is treated as a rule-of-law problem, not mere trial inconvenience

The concurrence’s first ground is anchored in Practice Book § 40-13 (a): when the defendant requests disclosure, the State must identify its witnesses within the required timeframe unless the court grants an extension for “good cause shown.” Justice Ecker emphasizes three aggravating features:

  • Non-disclosure despite request: The State did not disclose McCormack as an expert in response to the defendant’s pretrial disclosure motion.
  • Affirmative representation: The prosecutor assured in open court that no expert testimony would be offered.
  • No good-cause finding: The trial court made no finding of “good cause” to excuse the late expert disclosure, which State v. Mallozzi makes a prerequisite.

This reasoning treats the timing and notice function of discovery as substantive fairness protection: without notice, the defense cannot investigate the expert’s qualifications, challenge methodology, prepare rebuttal experts, or calibrate cross-examination strategy.

B. “Opening the door” cannot substitute for discovery compliance

Justice Ecker rejects the prosecutor’s claim that defense questioning about the defendant’s favorable treatment of the victim “opened the door” to grooming expert testimony. Relying on State v. Payne and State v. Graham, the concurrence explains:

  • The doctrine prevents a party from exploiting selective admission after successfully excluding otherwise admissible contextual evidence; it does not authorize introduction of “unrelated matters.”
  • Routine cross-examination on the nature of the relationship in a sexual-assault case is foreseeable and does not justify midtrial expert surprises.
  • The doctrine cannot be converted into a mechanism for “injection of prejudice” or for evading disclosure rules.

C. Hybrid witnesses create structural risks that require active judicial management

The concurrence’s second ground is not that hybrid testimony is per se inadmissible, but that it is intrinsically risky—especially with law enforcement—because of the credibility premium jurors give police and experts. Drawing heavily on United States v. Cruz, United States v. Williams, and State v. Raynor, Justice Ecker identifies the core dangers:

  • Credibility spillover: The “aura” of expertise may cause jurors to over-credit factual assertions.
  • Role confusion: Jurors may not know when the witness is describing observed facts, giving lay opinions, or offering expert conclusions.
  • Instructional backfire: A generic expert instruction can inadvertently “upgrade” all opinions to expert status.

The concurrence then lists concrete measures recognized by federal authority—special jury instructions, structured sequencing, careful foundational distinctions, and avoiding court-endorsed “expert” labeling—but notes that none were used here.

D. A caution about judicial prompting

Finally, the concurrence adds a process-based caution: the trial court’s question (“some type of expert witness”) may have influenced the State’s decision to pursue expert designation midtrial. While not a separate ground of error, it underscores the concurrence’s theme that expert testimony should be deliberately managed and disclosed—not improvised.

3.3 Impact

A. Trial-court gatekeeping and enforcement of expert discovery

Although a concurrence is not the majority’s holding, Justice Ecker’s reasoning functions as an institutional warning: Connecticut trial courts should treat late-disclosed expert testimony—particularly by the State—as presumptively problematic absent an explicit, record-based “good cause” finding consistent with State v. Mallozzi. The opinion also signals that repeated failures may warrant systemic reform, echoing Mallozzi’s suggestion that the Rules Committee consider “a more formalized expert disclosure process.”

B. Managing “grooming” testimony in child/sexual-assault prosecutions

The concurrence flags “grooming” as an area where courts nationally diverge on whether expert testimony is necessary (In re Personal Restraint of Phelps vs. Morris v. State). Connecticut litigants can expect future disputes over:

  • Whether grooming is within common juror understanding or requires expert explanation;
  • How to police the boundary between permissible behavioral-context testimony and impermissible profiling or propensity reasoning;
  • What foundations, limits, and instructions are required if grooming testimony is admitted.

C. “Hybrid witness” safeguards as best practices

By compiling federal “measures” (instructions, structuring, foundation, careful labeling), the concurrence offers a practical checklist that defense counsel may cite in motions in limine and that trial courts may adopt to reduce reversible error risk. Even where hybrid testimony is allowed, failure to employ safeguards is framed as a factor supporting abuse-of-discretion review.

4. Complex Concepts Simplified

Key Terms

  • Expert disclosure (Practice Book § 40-13 (a)): When the defense requests it, the prosecution must identify witnesses—including experts—within required timelines. Late identification is allowed only if the court extends time for “good cause shown.”
  • Good cause: A legitimate, case-specific reason for a delay (e.g., new evidence that truly could not have been anticipated earlier). It must be shown on the record and, as the concurrence stresses, found by the court.
  • Opening the door: A fairness doctrine allowing otherwise inadmissible contextual evidence only when a party has created a misleading impression by selective use or exclusion of evidence. It is not a general waiver of evidentiary or discovery rules.
  • Hybrid (dual-role) witness: A witness—often a police officer—who testifies both as a fact witness (what they did/saw in the investigation) and as an expert (opinions based on specialized knowledge). This can blur roles and inflate credibility.
  • Harmless error: Even if evidence was wrongly admitted, a conviction is affirmed if the appellate court has “a fair assurance that the error did not substantially affect the verdict” (State v. Ayala).

5. Conclusion

Justice Ecker’s concurrence in State v. Fomo (Concurrence) crystallizes two practice rules with broader significance: (1) expert testimony—especially by the prosecution—must be timely disclosed under Practice Book § 40-13 (a) absent a demonstrated and found “good cause,” and (2) when an investigating officer testifies as both fact witness and expert, the trial court must actively manage the heightened risks of juror confusion and undue credibility, using recognized safeguards. Although the concurrence agrees the error was harmless under State v. Ayala, its reasoning serves as a pointed caution that discovery compliance and careful handling of hybrid witnesses are essential to fair adjudication and to maintaining confidence in criminal verdicts.