Lopez v. People (2026 CO 23): Repeated “Coaching” Theory Opens the Door to Limited Expert Testimony of No Indicia of Coaching

I. Introduction

In Gustavo LOPEZ v. The PEOPLE of the State of Colorado, 587 P.3d 175 (Colo. 2026) (“2026 CO 23”), the Colorado Supreme Court considered the scope of Colorado’s “opening the door” doctrine in the context of a child sexual assault prosecution where the defense’s central theory was that the child complainants were “coached” or otherwise improperly influenced by their maternal grandmother.

The key evidentiary flashpoint arose after the prosecution presented forensic interviewer Kim Grimm as an expert. Following her generalized testimony about forensic interviewing—including indicators of coaching—a juror asked whether either child’s behavior in Grimm’s interviews was consistent with cases where coaching was present. Over defense objection, the trial court allowed the question, and Grimm responded that she did not see “huge red flags” indicating coaching, citing the children’s ability to provide “very specific experience-based details.”

On appeal, a split court of appeals division affirmed, holding the testimony was inadmissible but permissible as “door-opening” rebuttal. The Colorado Supreme Court granted certiorari on the door-opening question and affirmed.

Parties and posture

  • Petitioner/Defendant: Gustavo Lopez
  • Respondent/Prosecution: The People of the State of Colorado
  • Review of: People v. Lopez, 2024 COA 26, 550 P.3d 731

Core issue

Assuming the expert’s “no indicia of coaching” testimony was otherwise inadmissible, did the defense “open the door” to that testimony by repeatedly advancing a coaching theory—through evidence and argument—focused on a specific, identifiable coach (the maternal grandmother)?

II. Summary of the Opinion

The Court (Samour, J.) affirmed. It assumed without deciding that Grimm’s testimony was inadmissible and held that the defense nevertheless opened the door to it by persistently presenting evidence and argument that the children were coached or improperly influenced by their maternal grandmother to fabricate allegations or form false memories.

The Court emphasized two limiting principles:

  1. Narrow construction: “opening the door” must be narrowly applied; a mere credibility attack does not suffice.
  2. Proportionality: the “width of the opening dictates” the permissible scope of rebuttal; the opposing party may not “come storming through it in a pair of hobnailed boots.” (United States v. Sepulveda, 15 F.3d 1161, 1189 n.24 (1st Cir. 1993)).

Applying a deferential abuse-of-discretion review to the trial court’s determination, the Court found no manifest error in allowing a tightly confined response addressing whether Grimm observed indications of coaching.

III. Analysis

A. Precedents Cited

1. The doctrine’s national framing and Colorado’s “misleading impression” formulation

  • Warren Live Stock Co. v. Farr, 142 F. 116, 117 (8th Cir. 1905), quoted via McCormick on Evidence: the “fighting fire with fire” intuition—if a party opens an incompetent inquiry, it cannot complain when the opponent responds in kind. The Court used this framing to situate Colorado’s approach within a broader curative-admissibility tradition.

  • Bearint ex rel. Bearint v. Dorell Juv. Grp., Inc., 389 F.3d 1339, 1349 (11th Cir. 2004): cited for naming conventions (“curative admissibility,” “opening the door,” “fighting fire with fire”), reinforcing that the doctrine is widely recognized.

  • Hemphill v. New York, 595 U.S. 140, 152 (2022): cited for New York’s formulation requiring courts to assess whether a party created a “misleading impression” requiring correction. The Colorado Supreme Court treated Colorado’s doctrine as largely speaking the same language.

  • People v. Melillo, 25 P.3d 769, 775 (Colo. 2001): invoked as a Colorado example using the “opening the door” label, anchoring the doctrine in Colorado jurisprudence.

  • People v. Murphy, 919 P.2d 191, 195 (Colo. 1996): used to articulate the core trigger—selective presentation that creates an incorrect or misleading impression.

  • Golob v. People, 180 P.3d 1006, 1012 (Colo. 2008) (citing Murphy): the Court’s principal operational precedent. Golob held that once one side is allowed to present an incomplete or one-sided account (there, expert interpretation of the other expert’s report), fairness requires allowing otherwise inadmissible evidence to supply context and prevent “unfair advantage.”

  • People v. Miller, 890 P.2d 84, 98–99 (Colo. 1995): cited for the doctrine’s purpose—preventing unfair advantage through selective facts that mislead absent context.

2. Standard of review and expert-testimony gatekeeping

  • People v. Johnson, 2021 CO 35, ¶¶ 15–16, 486 P.3d 1154, 1158: supplied the dual framework: contours of the doctrine reviewed de novo, but the trial court’s “opened the door” determination reviewed for abuse of discretion.

  • People v. Coons, 2021 CO 70, ¶ 41, 495 P.3d 961, 969: cited for abuse-of-discretion review of expert testimony admission.

  • People v. Rector, 248 P.3d 1196, 1200 (Colo. 2011): quoted via Coons for the “manifestly erroneous” benchmark for reversal.

  • People v. Cooper, 2021 CO 69, ¶ 93, 496 P.3d 430, 447: cited for the deference owed to trial courts’ on-the-ground judgment under abuse-of-discretion review.

3. The underlying (but unresolved here) admissibility dispute: coaching testimony vs. vouching

The majority deliberately did not decide whether “no indicia of coaching” testimony is admissible in the first place. It noted that the issue is “more nuanced” than three court of appeals divisions had assumed, and it highlighted tensions in Colorado case law.

  • People v. Bridges, 2014 COA 65, ¶ 16, 410 P.3d 512, 514–15, and People v. Heredia-Cobos, 2017 COA 130, ¶ 17, 415 P.3d 860, 864: the court of appeals decisions treated “no coaching” opinions as improper under CRE 608(a) (akin to opinion testimony that a witness told the truth on a particular occasion). The majority discussed these cases to explain the division’s “first rung” of inadmissibility, while refusing to endorse it.

  • Venalonzo v. People, 2017 CO 9, ¶ 67, 388 P.3d 868, 885–86 (Coats, J., concurring in the judgment): cited for the proposition that the scope of the “no vouching” rule is “somewhat unclear.”

  • In the notes, the majority juxtaposed lines of authority including People v. Snook, 745 P.2d 647 (Colo. 1987), People v. Wittrein, 221 P.3d 1076 (Colo. 2009), and Venalonzo v. People (as CRE 608(a)-centered skepticism toward credibility-implicating expert opinions), with People v. Gaffney, 769 P.2d 1081 (Colo. 1989), People v. Fasy, 829 P.2d 1314 (Colo. 1992), and People v Cooper, 2021 CO 69 (as CRE 702 permissiveness for generalized expert testimony that may incidentally bolster credibility).

  • The Court also relied on Liggett v. People, 135 P.3d 725, 732 n.2 (Colo. 2006), and Tippett v. Johnson, 742 P.2d 314, 315 (Colo. 1987), to reject deciding broader or hypothetical questions (e.g., whether door-opening can ever permit direct “told the truth” testimony).

4. Limits on the rebuttal response: proportionality and non-weaponization

  • People v. Cohen, 2019 COA 38, ¶ 23, 440 P.3d 1256, 1262: cited for the proposition that opening-the-door is not unlimited and must be confined to what is needed to cure unfair prejudice.

  • United States v. Sepulveda, 15 F.3d 1161, 1189 n.24 (1st Cir. 1993): cited to emphasize restraint and proportionality in rebuttal.

B. Legal Reasoning

1. The Court’s doctrinal setup: door-opening presupposes inadmissibility

A central structural move in the majority opinion is its insistence that, in Colorado, the doctrine “stirs to life only when the evidence in question is inadmissible.” Therefore, because Lopez sought review solely on door-opening (and the People did not cross-petition on admissibility), the Court assumed inadmissibility and proceeded directly to whether the defense’s conduct activated the doctrine.

2. What constituted “opening the door” in this case

The Court treated the defense’s “coaching by grandmother” theory as a persistent, case-wide effort that went beyond a generic credibility attack: it was repeatedly tied to a particular identifiable person (the maternal grandmother), a concrete alleged motive (custody), and a timeline (denials before living with grandmother; disclosures after).

Specifically, the majority relied on the defense’s:

  • Voir dire focus on suggestibility and adult influence of children (including a custody-themed hypothetical curtailed by the court);
  • Opening statement emphasis that children’s accounts “differ[ed] based on who ha[d] control over the children”;
  • Cross-examinations eliciting admissions suggesting pre-interview discussions with grandmother about what to say, desire to live with grandmother, and timing of disclosures;
  • Grandmother cross suggesting custody motive and delayed reporting;
  • Closing argument “hammering” the coaching/false memory theme.

3. Why Grimm’s answer was deemed curative rather than unfairly prejudicial

The Court reasoned that—given (a) unopposed generalized expert testimony about coaching indicators and (b) the defense’s repeated coaching theory— the juror’s question essentially requested a routine expert application of general principles to the case facts. Excluding Grimm’s response would, in the majority’s view, leave the jury with an incomplete and potentially misleading picture—i.e., allowing the defense to press coaching as the explanation without permitting the prosecution to present the interviewer’s trained observations on whether coaching indicators appeared.

The majority acknowledged the testimony was prejudicial but characterized it as not unfairly prejudicial in context: the rebuttal was narrowly confined (“no huge red flags,” “nothing that indicated that”) and responsive to the defense’s repeated insinuations.

4. The two limiting admonitions—now elevated as controlling guidance

The opinion’s most durable doctrinal content lies in its constraints:

  • Narrow trigger: door-opening does not arise from “simply” challenging credibility; it arose here from repeatedly suggesting coaching/improper influence by the grandmother.
  • Proportional cure: the “opening’s width” limits what may come in; courts must prevent rebuttal from turning into a “weaponized” overreach.

C. Impact

1. Practical effect in child sexual assault prosecutions

Although the Court avoided deciding whether “no indicia of coaching” opinions are admissible under CRE 608(a) or CRE 702, it nonetheless created a consequential procedural pathway: if such testimony is inadmissible, it may still come in through door-opening when the defense repeatedly advances a coaching-by-identifiable-person theory.

This will matter in credibility-centric cases—especially child sexual assault cases—where “coaching” theories are common. The majority’s approach encourages trial courts to:

  • Scrutinize whether the defense has moved from generic credibility attack to a specific, repeated coaching narrative;
  • Allow tightly constrained rebuttal through the prosecution’s expert (or other evidence) to counter the asserted misimpression;
  • Police proportionality carefully to avoid overbroad credibility vouching.

2. Increased importance of trial-level record-making

Because the “opened the door” determination is reviewed for abuse of discretion, litigants should expect appellate courts to defer heavily to trial judges’ assessments of: (a) how pervasive the “coaching” theme was, (b) whether it created a misleading impression, and (c) whether the rebuttal was proportionate. This places a premium on contemporaneous objections, limiting requests, and offers of proof about scope.

3. The unresolved substantive question remains live

The Court signaled doctrinal uncertainty about whether “no coaching” opinions are categorically equivalent to vouching—highlighting competing lines of authority (CRE 608(a) strictness versus CRE 702 permissiveness for generalized syndrome/behavior testimony). Future cases—especially those with a cross-petition or where admissibility is squarely presented—are likely to address that question directly.

4. The dissent’s warning: potential chilling of “coaching” defenses

The dissent (Márquez, C.J.) framed the majority’s holding as a significant expansion, arguing that it effectively allows otherwise inadmissible expert vouching to enter merely because the defense pursues a “garden-variety” coaching theory, including through voir dire/opening/closing (not evidence). The dissent’s concerns, even if not controlling, will likely shape future litigation over the doctrine’s boundaries and the legitimacy of using attorney argument (and trial themes) as the “misleading impression” that triggers curative admissibility.

IV. Complex Concepts Simplified

“Opening the door”
A fairness doctrine: if one side presents information in a way that risks misleading the jury, the judge may allow the other side to introduce otherwise inadmissible evidence to correct the misimpression. It is not a free pass to introduce anything; it is limited to what is needed to “cure.”
“Misleading impression” / “unfair advantage”
The idea that the jury could be steered toward a mistaken conclusion because it hears only part of the relevant picture (or hears facts without needed context). The doctrine is meant to prevent “selective presentation” that distorts the jury’s understanding.
CRE 608(a) (credibility/vouching limits)
Colorado generally bars witnesses—especially experts—from opining that another witness was truthful on a particular occasion, because credibility is for the jury. The admissibility fight here concerned whether saying “I saw no signs of coaching” is effectively the same as saying “they were telling the truth.” The majority did not decide that issue.
CRE 702 (expert testimony)
Allows expert testimony that helps jurors understand evidence or decide facts, but it cannot invade the jury’s role by directly telling them whom to believe. Colorado cases differ on how far experts can go when discussing behaviors consistent with abuse or inconsistent with fabrication.
Abuse of discretion
A highly deferential appellate standard. The trial court’s decision stands unless it was “manifestly erroneous.” In practice, this means many close calls about scope and fairness will be resolved at the trial level.

V. Conclusion

Lopez v. People establishes a practical rule of trial conduct in Colorado: when a defendant repeatedly advances a coaching theory tied to an identifiable person and motive—through evidence and argument—the defendant may “open the door” to otherwise inadmissible expert testimony that the interviewer observed no indication of coaching, provided the rebuttal remains narrowly confined to curing the asserted misimpression.

The Court simultaneously cautioned that the doctrine must be narrowly applied and proportionate in execution, attempting to prevent the curative exception from becoming a vehicle for broad credibility bolstering. Yet by resolving the case on door-opening while leaving admissibility unresolved, the decision also ensures continued litigation over the boundary between permissible “context” and impermissible vouching—particularly in child sexual assault cases where credibility is central.