“The Curtin Principle”: Express Agreement as Waiver and the ‘Commonsense’ Test for Expert Testimony under Rule 702

1. Introduction

United States v. Dana Curtin, No. 23-3368 (7th Cir. July 1, 2025), addresses two recurring trial-level questions: (i) when does a defendant’s concession in open court waive later appellate review, and (ii) at what point does proposed expert testimony become so self-evident that Rule 702 deems it unnecessary? Dana Curtin was convicted of attempted sex trafficking of a minor after extensive text communications with an undercover FBI agent. On appeal, he argued that the district court improperly excluded portions of a forensic psychiatrist’s testimony meant to show that he lacked “pedophilic tendencies” and that interest in adult commercial sex or adult pornography does not imply an interest in children.

The Seventh Circuit affirmed. It forged two doctrinal clarifications that practitioners must now heed:

Express Agreement Equals Waiver – Where counsel explicitly concurs with the trial judge’s ruling, the issue is waived, not merely forfeited, foreclosing appellate review.
The Commonsense Test for Rule 702 Helpfulness – Expert testimony explaining propositions that average jurors already grasp (e.g., “liking adult sex does not mean liking child sex”) may be excluded as unhelpful; such exclusion will be upheld unless manifestly erroneous.

2. Summary of the Judgment

Judge St. Eve, writing for a unanimous panel, held:

Waiver of Pedophilia Testimony – Defense counsel’s statement “I agree with you, Judge” regarding the irrelevance of pedophilia-diagnosis testimony constituted waiver. Because waiver is the “intentional relinquishment of a known right,” no appellate review was available.
Exclusion of ‘Adult vs. Child Interest’ Testimony – The district court did not abuse its discretion in finding Dr. Saleh’s proposed testimony unhelpful under Federal Rule of Evidence 702; the distinction between adult and child sexual interest is within common juror experience.
Harmlessness – Assuming arguendo error, the exclusion was harmless given overwhelming evidence of Curtin’s intent.

3. Analysis

3.1 Precedents Cited and Their Influence

United States v. Burns, 843 F.3d 679 (7th Cir. 2016) – Supplies the rule that objections must be “timely and specific.” The panel used Burns to underscore that Curtin’s positive affirmation lacked objection specificity.
United States v. Olano, 507 U.S. 725 (1993) – Distinguishes waiver from forfeiture; the opinion relied on Olano to show that waiver extinguishes error.
United States v. Flores, 929 F.3d 443 (7th Cir. 2019); United States v. Robinson, 964 F.3d 632 (7th Cir. 2020); United States v. McGhee, 98 F.4th 816 (7th Cir. 2024) – Each provided fact patterns where counsel’s “affirmative agreement” led to waiver. Curtin’s facts mirrored these.
Salem v. U.S. Lines Co., 370 U.S. 31 (1962) and United States v. Christian, 673 F.3d 702 (7th Cir. 2012) – Foundations of the “commonsense” doctrine. The panel invoked them to justify exclusion of unnecessary expert evidence.
General Electric v. Joiner, 522 U.S. 136 (1997); United States v. Tsarnaev, 595 U.S. 302 (2022) – Articulate the “manifestly erroneous” standard for reviewing evidentiary discretion. The panel framed its deference with these cases.
United States v. Dewitt, 943 F.3d 1092 (7th Cir. 2019) & Dhillon v. Crown Controls Corp., 269 F.3d 865 (7th Cir. 2001) – Affirm that jurors may apply life experience without expert input; relied on to label Dr. Saleh’s testimony “commonsense.”
United States v. Gan, 54 F.4th 467 (7th Cir. 2022); United States v. Boros, 668 F.3d 901 (7th Cir. 2012) – Provide the harmless-error / sufficiency framework used in the alternative analysis.

3.2 Legal Reasoning

Waiver Analysis – The court dissected the colloquy where defense counsel agreed that pedophilia-diagnosis testimony was precluded. Citing Burns, Olano, and Robinson, it concluded the agreement was a strategic, intentional act extinguishing appellate rights.
Rule 702 ‘Helpfulness’ Determination – Applying the Salem line of cases, the trial court asked: “Will this aid the jury beyond ordinary reasoning?” It decided jurors did not need expert instruction to know that sexual attraction to adults differs from attraction to minors.
Abuse-of-Discretion Standard – Referencing Joiner and Tsarnaev, the appellate panel reiterated that reversal demands a “manifest error.” Because the district court’s reasoning was plausible and careful (it even warned the government not to smuggle in its own quasi-expert testimony), no abuse existed.
Harmless Error – Even if exclusion were wrong, overwhelming evidence (ten-week texting, pictures exchanged, bringing $150 and condoms, arrival at meeting site) rendered any error non-prejudicial under Federal Rule of Criminal Procedure 52(a).

3.3 Impact of the Judgment

This decision is likely to reverberate in three principal arenas:

Trial Objections and Appellate Strategy – Counsel must now recognize that explicit concessions create iron-clad waiver in the Seventh Circuit. Merely remaining silent or saying “no objection” was risky before; post-Curtin, affirmatively agreeing is fatal.
Expert Testimony in Sexual-Offense Cases – Defendants frequently attempt to introduce psychiatric evidence negating pedophilic disorder. Curtin signals that such evidence is routinely irrelevant absent a government expert and that generalized “adult vs. child” distinctions are non-expert matters.
Rule 702 ‘Commonsense’ Doctrine Strengthened – The ruling reinforces that judges may exclude even scientifically sound testimony if it offers nothing beyond ordinary reasoning. Lawyers must therefore articulate a nuanced, non-obvious nexus between expert opinion and case-specific facts.

4. Complex Concepts Simplified

Waiver vs. Forfeiture
- Waiver: Intentional relinquishment of a right—issue dead on appeal.
- Forfeiture: Unintentional oversight—issue reviewed for “plain error.”
Federal Rule of Evidence 702
- Allows expert testimony only if it will help the jury by providing “scientific, technical, or other specialized knowledge.”
- “Helpfulness” is lacking when the subject is within a layperson’s everyday understanding.
Pedophilic Disorder (DSM-5)
- A clinical diagnosis requiring recurrent sexual fantasies/behaviors involving prepubescent children.
- Absence of the disorder does not preclude criminal intent toward minors, as the court noted.
CSAM – Acronym for “Child Sexual Abuse Material,” the preferred contemporary term for child pornography.
Manifestly Erroneous – A decision so incorrect that “no reasonable person” would agree with it; the high bar for reversing discretionary rulings.

5. Conclusion

United States v. Curtin cements two practical doctrines in Seventh Circuit jurisprudence: first, that an express on-the-record agreement with a trial ruling waives the issue for appeal; and second, that expert testimony repeating obvious, everyday propositions fails Rule 702’s helpfulness requirement. These holdings sharpen trial advocacy boundaries, especially in child-exploitation prosecutions where parties often seek to deploy psychiatric experts. Going forward, defense and prosecution alike must craft evidentiary strategies that either clearly preserve objections or unmistakably demonstrate why an expert’s perspective adds value beyond jurors’ common sense. Curtin thus stands as a concise but potent precedent on waiver doctrine and the outer limits of expert assistance.