Lopez v. People (2026 CO 23): Repeated “Coaching” Theory Can Open the Door to Otherwise Inadmissible Expert “No Indicia of Coaching” Testimony—Narrowly and Proportionally

1. Introduction

Parties: Gustavo Lopez (Petitioner/defendant) v. The People of the State of Colorado (Respondent/prosecution).
Court: Colorado Supreme Court (en banc).
Context: A child sexual assault prosecution hinging substantially on the credibility of two child witnesses, N.L. and A.L.

The prosecution introduced the children’s forensic interviews through Kim Grimm, the forensic interviewer, who was also qualified (without objection) to provide generalized expert testimony about child forensic interviewing, including what “coaching” is and what indicators interviewers are trained to look for. A juror asked whether either child’s behavior was consistent with coached interviews. Over defense objection, the trial court permitted Grimm to answer; she testified she did not see “huge red flags” indicating coaching.

On appeal, a division of the court of appeals held Grimm’s specific “no signs of coaching” opinion was inadmissible, but affirmed on the ground that the defense had “opened the door” by persistently advancing a coaching theory aimed at the children’s maternal grandmother. The Colorado Supreme Court granted review on the “opening the door” question.

2. Summary of the Opinion

The Colorado Supreme Court affirmed, holding that—assuming without deciding Grimm’s testimony was otherwise inadmissible—the defense “opened the door” to it by repeatedly suggesting, through evidence and argument, that the grandmother coached or improperly influenced the children to fabricate allegations or develop false memories to maintain custody.

The Court emphasized two limiting principles: (1) the opening-the-door doctrine must be applied narrowly; and (2) the “width of the opening” controls the scope of the responsive evidence admitted.

A dissent argued the testimony was classic impermissible vouching and that the majority improperly expanded “opening the door” to include counsel’s non-evidentiary statements (voir dire, openings, closings) and ordinary credibility-based defense theories.

3. Analysis

A. Precedents Cited

1) The opening-the-door doctrine: definition, purpose, and limits

  • People v. Melillo: Cited as Colorado authority recognizing “opening the door.” The majority uses it to situate the doctrine within Colorado practice and terminology.
  • People v. Murphy: Used for the “misleading impression” framing—opening the door is triggered when selective presentation creates an incorrect or misleading impression requiring contextual correction.
  • Golob v. People: The majority’s central Colorado example. There, the Court held it was unfair for one side’s expert characterization to stand “unchallenged”; once one party injects a partial picture, the other may supply otherwise barred context to prevent unfair advantage. Lopez draws a direct analogy: the defense pressed coaching; Grimm’s “no indication” testimony supplied the contextual counterpoint.
  • People v. Miller: Cited for the doctrine’s fairness rationale—preventing a party from gaining and maintaining an unfair advantage via selective facts. The majority treats Lopez’s repeated coaching narrative as creating a one-sided “coin” absent Grimm’s response.
  • Hemphill v. New York: Not applied as binding state evidentiary law here, but used to illustrate the national “misleading impression” approach and to underscore that Colorado “largely speaks the same language.”

2) Standard of review and trial-court discretion

  • People v. Johnson: Supplies the review framework: doctrine’s contours construed de novo; the trial court’s “opened the door” determination reviewed for abuse of discretion.
  • People v. Coons: Confirms abuse-of-discretion review for admission of expert testimony; later used to explain the deference owed absent “manifest” error.
  • People v. Rector: Quoted (through Coons) for the “manifestly erroneous” abuse-of-discretion threshold.
  • People v. Cooper: Cited for the institutional reason for deference—appellate courts should not second-guess the trial court’s on-the-ground judgment.

3) Proportionality—how far the response may go

  • United States v. Sepulveda and People v. Cohen: The majority adopts Sepulveda’s memorable constraint (“hobnailed boots”) via Cohen: opening the door does not authorize an unlimited, weaponized response; rebuttal must stay confined to what is necessary to address the unfair advantage created.

4) The admissibility issue the majority reserves (but flags as unsettled)

  • People v. Bridges and People v. Heredia-Cobos: The court of appeals relied on these to deem “no coaching” opinions inadmissible under CRE 608(a) as tantamount to vouching. The majority notes those divisions treated the issue as settled, but cautions the question is “more nuanced” than those opinions recognized.
  • Venalonzo v. People: Quoted for the proposition that the scope of the anti-vouching principle has “always been somewhat unclear,” reinforcing that the “no coaching” question is not cleanly resolved.
  • Liggett v. People and Tippett v. Johnson: Cited to justify restraint—declining to decide broader questions not presented and avoiding advisory opinions.
  • People v. Snook, People v. Wittrein, People v. Gaffney, People v. Fasy, and People v. Relaford (and People v. Koon via Cooper/Relaford): Appearing in the majority’s footnote comparison, these illustrate tension in Colorado doctrine between (a) CRE 608(a) limits on credibility/vouching and (b) CRE 702 permission for generalized expert testimony that may incidentally bolster credibility.

5) The dissent’s credibility/vouching line of cases and doctrinal boundary arguments

  • People v. Eppens, Tevlin v. People, People v. Oliver, People v. Baker, and People v. Wittrein: The dissent relies on these to argue the “no coaching” opinion is indistinguishable from impermissible truth-telling testimony—an invasion of the jury’s credibility function.
  • Medina v. People, People v. Cole, People v. Tenorio, People v. Sams, and People v. Miller: The dissent reads these as limiting opening-the-door to situations where one party creates an objectively misleading inference and blocks rebuttal—conditions it says were absent here.
  • Pernell v. People and Davis v. People: Cited by the dissent to caution against treating openings/closings as “opening the door,” since they are not evidence.
  • People v. Ray, People v. Kembel, and People v. Dist. Ct.: Invoked to argue the doctrine cannot be used to inject unfair prejudice—especially where credibility is the focal issue.

B. Legal Reasoning

  1. Step one: the doctrine applies only to otherwise inadmissible evidence. The Court reiterates (explicitly, via its definition and its footnote on imprecision) that “opening the door” is a curative doctrine permitting otherwise inadmissible evidence when selective presentation creates an inaccurate or misleading impression. Because the People did not cross-petition the court of appeals’ inadmissibility ruling, the Supreme Court assumes without deciding Grimm’s “no indication of coaching” answer was inadmissible and proceeds directly to the door-opening analysis.
  2. Step two: identifying the “selective presentation” creating the misimpression. The majority treats the defense’s sustained coaching theory—advanced through voir dire, opening statement, cross-examination, and closing argument—as a sustained effort to persuade jurors the allegations were fabricated or memory-contaminated due to grandmother’s influence. The Court characterizes this as presenting only “one side of the coaching coin” absent responsive contextual evidence.
  3. Step three: why Grimm’s answer is a permitted “context” response. Because Grimm had already given generalized expert testimony about what coaching is and what signs interviewers look for (without objection), the juror’s question effectively asked her to apply those general principles to the children’s interviews. The Court reasons that barring Grimm from answering would have produced an “unfair advantage” for the defense by allowing the coaching narrative to stand without the contextual counterpoint from the same witness who explained coaching indicators.
  4. Step four: proportionality and narrowness. The Court underscores that merely challenging credibility does not open the door; the door opened here because the defense repeatedly asserted a concrete coaching/improper-influence theory tied to an identifiable person (the grandmother). It then adds the proportionality constraint: the prosecution may not “storm[] through” the opening; responsive evidence must be limited to what is necessary to cure the prejudice created. On the record, the Court finds the trial judge kept the response “tightly confined in scope.”

C. Impact

  • Doctrinal clarification (and practical consequence): Lopez is now a leading Colorado Supreme Court statement that repeatedly advancing a coaching/improper-influence theory through evidence and argument can “open the door”—even to testimony assumed to be otherwise inadmissible—so long as it is used to correct a misleading impression and is proportionate to the opening.
  • Litigation strategy in child sexual assault cases: Defense counsel who intend to argue coaching must anticipate that an interviewer-expert may be permitted to give a case-specific “no indicia” response if the defense presentation is persistent and concrete. Conversely, prosecutors will cite Lopez to justify narrowly tailored case-application testimony after a coaching narrative is developed.
  • Limits emphasized but contested: The majority’s admonitions (narrow construction; proportional scope) will be central in future disputes. The dissent forecasts defendants will argue Lopez chills ordinary credibility defenses and improperly treats non-evidence (voir dire/opening/closing) as door-opening conduct—an issue likely to recur in later cases testing Lopez’s boundaries.
  • Unresolved admissibility question remains open: The Court deliberately leaves unsettled whether “no coaching” testimony is admissible in the first instance under CRE 608(a)/CRE 702. Future cases may squarely decide whether such testimony is impermissible vouching or permissible expert assistance that only incidentally bolsters credibility.

4. Complex Concepts Simplified

“Opening the door”
A fairness doctrine: if one side introduces information in a way that leaves the jury with a misleading picture, the judge may allow the other side to introduce otherwise inadmissible evidence to correct that misimpression. In Lopez, the Court treated the defense’s repeated coaching narrative as creating a one-sided picture that justified a limited corrective response.
Vouching / credibility opinions (CRE 608(a))
Generally, witnesses—especially experts—cannot tell the jury that another witness was truthful on a specific occasion, because credibility is for the jury to decide. The court of appeals viewed “no signs of coaching” as too close to “the child is telling the truth.” The Supreme Court did not decide that question, but assumed inadmissibility for purposes of applying the door-opening doctrine.
Abuse of discretion
A deferential appellate standard. Even if appellate judges might have ruled differently, they will uphold the trial judge unless the decision was “manifestly erroneous.” Lopez relies heavily on this deference in affirming the admission of the limited testimony.
Proportionality (“width of the opening”)
Even when the door is opened, the response must be limited. The opposing party may introduce only what is needed to cure the unfairness—not everything that becomes rhetorically useful.

5. Conclusion

Lopez v. People establishes that when a criminal defendant repeatedly advances a coaching/improper-influence theory—through evidence and argument—Colorado trial courts may treat that presentation as “opening the door” to a narrowly confined expert response that the interviewer perceived no indication of coaching, even assuming such testimony would otherwise be inadmissible.

The decision’s significance lies less in resolving the underlying vouching/admissibility debate (which the Court expressly leaves open) and more in its practical guidance on the curative admissibility doctrine: apply it narrowly, and ensure the prosecution’s rebuttal fits the opening. The dissent signals that future litigation will likely focus on whether Lopez’s conception of “misleading impression” and its reliance on counsel’s arguments unduly expand a doctrine meant to cure evidentiary unfairness—not to decide credibility by expert proxy.