United States v. Middleton: Trauma-and-Memory Expert Testimony Under Rule 702 and Jail-Call “Substantial Step” Attempted Obstruction Under 18 U.S.C. § 1591(d)

I. Introduction

In United States v. Middleton (1st Cir. May 8, 2026), the First Circuit affirmed convictions for (1) sex trafficking by force, fraud, or coercion under 18 U.S.C. § 1591(a)(1) and (b)(1), and (2) obstruction of a sex trafficking prosecution under 18 U.S.C. § 1591(d), based largely on recorded jail calls. The court also affirmed a 30-year sentence (360 months) and dismissed an ineffective assistance claim as premature.

The case arose from a four-day period in November 2015 in which the victim, Adrienne Rush, was subjected to forced commercial sex acts and repeated physical and sexual abuse. Years later, after Middleton’s 2022 arrest, prosecutors added an obstruction count when Middleton, from custody, repeatedly urged a friend to relay messages to co-defendant Sherry Jones to deny being present at a key location (Kafia Figaro’s house) or to claim lack of recall—conduct the government framed as an attempt to interfere with the prosecution.

On appeal, Middleton challenged: (1) the admission of expert testimony about trauma’s impact on memory; (2) the sufficiency of evidence for attempted obstruction; (3) the reasonableness of the sentence (especially disparity with co-defendants and the post–Adam Walsh Act guideline structure); and (4) trial counsel’s failure to cross-examine a witness.

II. Summary of the Opinion

  • Expert testimony affirmed: The district court did not abuse its discretion under Federal Rule of Evidence 702 by admitting Dr. James Hopper’s testimony about the neurobiology of trauma and its effects on memory. The testimony was deemed beyond the “ken” of lay jurors and did not impermissibly invade the jury’s credibility function.
  • Obstruction conviction affirmed: The recorded jail calls, combined with witness testimony, permitted a rational jury to find attempted obstruction under 18 U.S.C. § 1591(d). Repeated requests to relay instructions to a co-defendant constituted a “substantial step,” not mere preparation.
  • Sentence affirmed: Procedural unreasonableness was deemed waived for lack of developed argument. The within-Guidelines 360-month sentence was substantively reasonable; disparities with co-defendants were justified because they were not “identically situated.”
  • Ineffective assistance dismissed without prejudice: The court followed its usual practice of declining to consider fact-bound Sixth Amendment claims on direct appeal, leaving the claim for a potential 28 U.S.C. § 2255 proceeding.

III. Analysis

A. Precedents Cited

1. Standards of Review and Appellate Framing

  • United States v. Díaz-Rosado, 857 F.3d 116 (1st Cir. 2017): Used for the standard “light most favorable to the prosecution” framing when assessing sufficiency challenges.
  • United States v. Pires, 138 F.4th 649 (1st Cir. 2025): Central to the expert-testimony discussion (what is beyond the “ken” of laypersons) and sufficiency-review methodology; also cited regarding preserved objections and the relevance of expert evidence to credibility without usurping the jury.
  • United States v. Jackson, 58 F.4th 541 (1st Cir. 2023) and Martínez v. United States, 33 F.4th 20 (1st Cir. 2022): Explained the First Circuit’s “classic abuse-of-discretion review” and when judgment calls warrant reversal.

2. Expert Testimony: Rule 702, “Ken,” and Credibility

  • Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993): Provided the “gatekeeping” framework: expert evidence must be reliable and relevant to the task at hand; also invoked for the idea that cross-examination and instructions address “shaky but admissible evidence.”
  • United States v. Alzanki, 54 F.3d 994 (1st Cir. 1995): Key precedent approving expert testimony on “behavioral reactions of abuse victims,” recognizing such matters can be technical and beyond lay knowledge, and emphasizing jury instructions that preserve the jury’s freedom to reject expert views.
  • United States v. Montas, 41 F.3d 775 (1st Cir. 1994): Cited for the “common sense inquiry” guiding whether a topic is within ordinary experience.
  • Aetna Life Ins. Co. v. Ward, 140 U.S. 76 (1891): Used to underscore the traditional principle that credibility belongs to the jury, rooted in jurors’ “practical knowledge of men and the ways of men.”
  • United States v. Shay, 57 F.3d 126 (1st Cir. 1995): Supplied the limiting principle: expert testimony is not inadmissible merely because it bears on credibility; it can be allowed where it dispels “common myths” relevant to how jurors may misinterpret evidence.
  • United States v. Teganya, 997 F.3d 424 (1st Cir. 2021): Cited for waiver of an argument not pursued on appeal (here, Rule 403).
  • United States v. Soler-Montalvo, 44 F.4th 1 (1st Cir. 2022): Appeared within Pires’s collected examples of permissible beyond-lay-knowledge topics (e.g., grooming behavior), supporting the analogy to trauma-and-memory science.

3. Attempted Obstruction and “Substantial Step” Doctrine

  • United States v. Santonastaso, 100 F.4th 62 (1st Cir. 2024): Provided the sufficiency standard: whether a rational factfinder could find guilt beyond a reasonable doubt based on the evidence and plausible inferences.
  • United States v. Pérez-Rodríguez, 13 F.4th 1 (1st Cir. 2021): Set out attempt’s two elements: specific intent plus a substantial step toward completion.
  • United States v. Doyon, 194 F.3d 207 (1st Cir. 1999): Furnished the key attempt framing: distinguishing “mere preparation” from conduct that shows the defendant has moved down a path “reasonably calculated to end in the substantive offense.”
  • United States v. Dworken, 855 F.2d 12 (1st Cir. 1988): Supported the inference of intent and corroboration from repeated conduct—here, repeated calls and repeated requests to relay a coordinated message.
  • United States v. Farah, 766 F.3d 599 (6th Cir. 2014) and Staples v. United States, 511 U.S. 600 (1994): Used to resolve mens rea for 18 U.S.C. § 1591(d) (the court adopting “knowingly,” consistent with how courts supply mens rea when a statute is silent).

4. Sentencing Review, Disparity, and Waiver

  • United States v. Candelario, 105 F.4th 20 (1st Cir. 2024) and United States v. Zannino, 895 F.2d 1 (1st Cir. 1990): Anchored waiver principles: undeveloped arguments are treated as waived, including vague procedural-reasonableness claims.
  • United States v. Ayala-Vazquez, 751 F.3d 1 (1st Cir. 2014): Confirmed abuse-of-discretion review for substantive reasonableness and rejected the idea that a defendant is entitled to a lighter sentence solely because co-defendants received lighter sentences.
  • United States v. Otero, 155 F.4th 78 (1st Cir. 2025): Provided the “plausible rationale/defensible result” standard and the principle that within-Guidelines sentences are “almost always” defensible.
  • United States v. De La Cruz, 91 F.4th 550 (1st Cir. 2024) and United States v. Grullon, 996 F.3d 21 (1st Cir. 2021): Emphasized that disparity comparisons require “identically situated” defendants—rare in practice.
  • United States v. Robertson, 162 F.4th 209 (1st Cir. 2025): Reinforced that different plea postures, cooperation, conviction counts, and enhancements justify disparities.
  • United States v. Rodríguez-Adorno, 852 F.3d 168 (1st Cir. 2017): Cited for the practice of assuming the more favorable standard (abuse of discretion) where it would not change the outcome.
  • United States v. Millán-Machuca, 991 F.3d 7 (1st Cir. 2021): Invoked for the proposition that imposing a law-required sentence is not “unreasonable.”

5. Ineffective Assistance on Direct Appeal

  • United States v. Reyes-Ballista, 146 F.4th 100 (1st Cir. 2025) and United States v. Padilla-Galarza, 990 F.3d 60 (1st Cir. 2021): Articulated the First Circuit’s near-categorical rule: ineffective assistance claims generally should be raised via 28 U.S.C. § 2255, not on direct appeal, absent an applicable exception.

B. Legal Reasoning

1. Rule 702: Trauma-and-Memory Expert Testimony as Beyond Lay “Ken”

The court upheld the district judge’s relevance-and-helpfulness finding under Rule 702(a) by treating the neurochemical and brain-structure discussion (prefrontal cortex, hippocampus, and memory encoding under traumatic stress) as outside ordinary juror experience. Relying on Pires, Montas, and especially Alzanki, the panel analogized trauma-memory science to other expert domains routinely found beyond lay knowledge.

Crucially, the district court had narrowed the testimony: it excluded “reflex responses and habit responses,” excluded broader testimony about different ways brains respond to trauma, and barred hypotheticals “divorced from established facts,” to avoid speculation and undue influence on credibility determinations. The First Circuit treated that tailoring as confirming—rather than undermining—the Rule 702 exercise.

2. Credibility Boundary: Permissible “Credibility-Relevant” Science Without Vouching

Middleton’s principal fear was that the testimony functioned as an “excuse” for the complainant’s inconsistencies. The panel addressed this by drawing a sharp line: experts may educate jurors about phenomena that affect perception or memory (Shay), but may not opine that a particular witness is telling the truth (Aetna Life Ins. Co. v. Ward’s credibility principle). Dr. Hopper was a “blind expert,” never interviewed Rush, and gave general scientific testimony rather than a witness-specific credibility assessment.

The court also leaned heavily on limiting instructions, quoting the judge’s repeated direction that credibility belonged to jurors alone and that expert testimony could be accepted or rejected. This is consistent with Alzanki and with Daubert’s premise that adversarial tools and instructions mitigate risk.

3. Attempted Obstruction Under 18 U.S.C. § 1591(d): Repeated Jail Calls as a “Substantial Step”

The panel treated the obstruction conviction as one for attempt (matching the government’s closing argument and the court’s framing). Applying Pérez-Rodríguez and Doyon, it held that repeated instructions to relay a coordinated denial to a co-defendant were “reasonably calculated” to interfere with a prosecution and thus exceeded mere preparation. The repeated nature of the communications supported intent and corroboration (Dworken).

On mens rea, the court adopted “knowingly” as the appropriate standard for § 1591(d), citing United States v. Farah (which itself invoked Staples v. United States), thereby situating § 1591(d) within mainstream interpretive practice for silent mens rea statutes.

The defense argument that it was unclear who the messages targeted failed because witness testimony identified Jones as the intended recipient. The court emphasized the limits of sufficiency review: it would not reweigh credibility (Pires), only ensure the verdict was rational.

4. Sentencing: Waiver of Procedural Claims and Narrow Scope for Disparity Attacks

The First Circuit refused to entertain procedural-reasonableness challenges because Middleton did not identify a specific procedural error, invoking Candelario and Zannino (undeveloped arguments are waived). On substantive reasonableness, the court relied on Otero’s “plausible rationale/defensible result” benchmark and the presumption-like defensibility of within-Guidelines sentences.

For disparity arguments, the panel enforced the “identically situated” requirement from De La Cruz and Grullon, and found the defendants plainly not identical: Middleton went to trial, had a record, received leadership adjustments, and was convicted of obstruction. Ayala-Vazquez and Robertson reinforced that plea/cooperation and enhancement differences commonly justify disparate outcomes.

Middleton’s attempt to leverage the Adam Walsh Act’s increased penalties (and guideline amendment dynamics) did not establish unreasonableness. The court treated the argument as disconnected from the individualized § 3553(a) inquiry and from the “implausible rationale/indefensible result” standard.

5. Ineffective Assistance: Deferred to Collateral Review

Following Reyes-Ballista and Padilla-Galarza, the court dismissed Middleton’s claim—premised on failure to cross-examine—without prejudice, leaving it for § 2255 where a record can be developed about strategy, prejudice, and performance.

C. Impact

  • Rule 702 in sex-trafficking/sexual-violence trials: The decision strengthens the acceptability (in the First Circuit) of carefully cabined trauma-and-memory neuroscience testimony, especially when the expert is “blind,” the district court excludes hypotheticals untethered to facts, and the court gives explicit credibility instructions.
  • Obstruction theory under § 1591(d): The ruling signals that “attempted obstruction” can be proved through repeated jail communications aimed at coordinating witness/co-defendant statements, even when the defendant uses an intermediary. It clarifies that such conduct can qualify as a “substantial step” when it is operational (repeated, directive, and targeted), not merely aspirational.
  • Sentencing disparity challenges: The opinion reiterates that disparity arguments are difficult absent truly “identically situated” comparators and that trial posture and added counts (like obstruction) matter greatly.
  • Appellate practice: The procedural-waiver holding underscores the necessity of specifying procedural errors with developed argumentation; otherwise, appellate courts may address only substantive reasonableness.

IV. Complex Concepts Simplified

  • “Ken” of laypersons: A shorthand for what ordinary jurors are expected to know without expert help. If a topic is beyond that everyday knowledge, expert testimony is more likely to “help the trier of fact” under Rule 702(a).
  • Daubert “gatekeeping”: The judge must ensure expert testimony is both reliable (sound methods) and relevant (actually assists the jury on an issue).
  • “Blind expert”: An expert who does not evaluate the particular victim or facts directly; they testify to general scientific principles. This can reduce (though not eliminate) the risk the expert is perceived as vouching for a witness.
  • Credibility vs. credibility-relevant evidence: Experts generally cannot say “this witness is telling the truth,” but can explain scientific or psychological phenomena that jurors might otherwise misunderstand when evaluating testimony.
  • Attempt and “substantial step”: Attempt liability requires intent plus an action that strongly corroborates intent and moves beyond preparation—conduct that is meaningfully aimed at completing the crime.
  • Procedural vs. substantive reasonableness: Procedural concerns the steps and calculations (e.g., guideline computation, explaining the sentence). Substantive concerns whether the final sentence is too harsh or too lenient given the total circumstances.
  • Waiver for lack of development: If an appellant gestures at an argument without specifying errors and supporting them, the appellate court may deem it abandoned.

V. Conclusion

United States v. Middleton affirms two important operational points in First Circuit practice: (1) trauma-and-memory neuroscience can be admissible under Rule 702 when it genuinely exceeds lay understanding and is tightly limited to avoid vouching, and (2) repeated jail-call efforts to coordinate false or evasive accounts through an intermediary can constitute a “substantial step” supporting attempted obstruction under 18 U.S.C. § 1591(d). The opinion also reinforces strict waiver principles for undeveloped procedural sentencing claims and preserves the circuit’s strong preference for litigating ineffective assistance claims via § 2255 rather than on direct appeal.