“Speak Now or Forever Waive It” – The Fourth Circuit’s Specific-Objection Rule for Source-Code Attacks on Probabilistic DNA Software
(United States v. Brandon Chavis & Melissa Beasley, 4th Cir. 2025)

1. Introduction

The Fourth Circuit’s unpublished decision in United States v. Chavis and its companion appeal by Melissa Beasley arises from a string of armed robberies in the Norfolk, Virginia area in October 2021. A federal jury convicted Brandon Chavis of five Hobbs Act robberies, conspiracy, and related § 924(c) firearms counts; Beasley was convicted on all but two counts. On appeal, Chavis principally attacked the admission of expert testimony derived from TrueAllele, a probabilistic genotyping software, insisting that its undisclosed source code rendered the methodology unreliable under Daubert. He also raised sufficiency-of-the-evidence and indictment-variance arguments. Beasley challenged only the sufficiency of the evidence.

The Fourth Circuit (Judge Benjamin for a unanimous panel) affirmed. The Court declined to reach the merits of the TrueAllele debate, holding that Chavis waived the specific “source-code” objection by failing to articulate it below. It also found the circumstantial and digital evidence “crushing,” easily meeting the Jackson v. Virginia standard, and dismissed the variance claim as meritless.

2. Summary of the Judgment

• Expert Evidence: The Court held that because defense counsel failed to object at the Daubert hearing or at trial on the specific ground that the expert had not reviewed TrueAllele’s source code, the argument was not preserved for appellate review.
• Sufficiency of Evidence: Viewing the record in the light most favorable to the government, cell-tower data, surveillance video, DNA likelihood ratios, recovered clothing and weapons, and Beasley’s redemption of a stolen lottery ticket provided substantial evidence for all convictions.
• Indictment Variance: Any mismatch between the cover sheet (which referenced “attempted” robbery) and the body of the superseding indictment (charging only completed robberies) was non-prejudicial; the jury convicted on the exact offenses charged in the operative counts.
• Outcome: All convictions affirmed.

3. Analysis

3.1 Precedents Cited and Their Influence

• Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993) – Framework for admissibility of expert testimony. Cited to show the governing standard, but ultimately bypassed because the objection was deemed forfeited.
• Federal Rule of Evidence 702 – Establishes that expert testimony must be reliable and helpful. Again, relevant but not dispositive given waiver.
• Jackson v. Virginia, 443 U.S. 307 (1979) – Articulates the deferential sufficiency-of-the-evidence standard (“any rational trier of fact”). Forms the backbone of the panel’s rejection of both appellants’ sufficiency arguments.
• United States v. Zayyad, 741 F.3d 452 (4th Cir. 2014) – Reinforces the principle that objections must be made on the same grounds below to be preserved on appeal.
• United States v. Osborne, 514 F.3d 377 (4th Cir. 2008) – Confirms that convictions may rest solely on circumstantial evidence.
• Other citations (e.g., Banks, Redd) clarify constructive-amendment doctrine and the harmless nature of ordinary variances.

3.2 The Court’s Legal Reasoning

1. Waiver of Source-Code Challenge
   The panel stressed a bedrock rule: an appellate court will not consider arguments first raised on appeal unless extraordinary circumstances exist. At the Daubert hearing, defense counsel asked only a generalized question about whether the expert “knew what the program was actually doing.” Counsel never argued that lack of source-code review undermined reliability. Because preservation requires the same legal ground, the specific source-code objection was forfeited. Result: the Court “decline[d] to address the merits.”
2. Sufficiency of Evidence
   a. Digital Evidence: Cell-tower CDRs placed both defendants near every robbery, and text messages (“Its almost time to move baby wya”) linked them temporally.
   b. Physical & Forensic Evidence: Matching clothing (orange reflective vest, inside-out hoodie, brown boots), the rare Hi-Point 9 mm with a yellow-tipped sight, and a TrueAllele match “33 trillion times more probable” than coincidence tied Chavis to the scene.
   c. Consciousness of Guilt: Deletion of Beasley’s October data, her cashing of a stolen lottery ticket within 30 minutes, and the mobile-phone photograph of a soon-to-be-robbed Subway supported an inference of knowing participation.
   The Court reiterated that circumstantial evidence can be “crushing,” and appellate courts must afford the government every reasonable inference.
3. Variance Claim
   The crime charged (completed Hobbs Act robbery) was the crime tried and the crime on which the jury was instructed and returned verdicts. Any discrepancy on a cover page is a non-fatal clerical variance causing no prejudice.

3.3 Impact of the Decision

• Procedural Precedent: Defendants who wish to attack proprietary probabilistic DNA tools must raise specific objections—e.g., lack of source-code access—at the Rule 702/Daubert stage. Silent defendants cannot resurrect the argument on appeal.
• Evidentiary Implications: The decision tacitly approves the growing prosecutorial reliance on CDR mapping, digital photos, and probabilistic genotyping, so long as foundational objections are timely addressed.
• Conspiracy and Aiding-&-Abetting Cases: The judgment reinforces that repeated digital proximity, coordinated messaging, and vehicle usage may suffice to convict a non-shooter getaway driver or facilitator.
• Litigation Strategy: Defense counsel must build a granular record—requesting source-code discovery, subpoenaing validation data, and pressing the court for gatekeeping findings—or risk waiver.
• Future Appeals: Expect litigants to distinguish Chavis by demonstrating that they did raise the source-code issue below, thereby forcing appellate courts to confront the substantive reliability of opaque AI-driven forensic tools.

4. Complex Concepts Simplified

Probabilistic Genotyping (TrueAllele)

Software that uses statistical algorithms to interpret mixed or low-quantity DNA samples. Instead of a human analyst declaring a “match,” the program calculates a likelihood ratio (e.g., “33 trillion times more probable that the DNA belongs to Chavis than to a random person”).

Source Code

The human-readable instructions that tell the software exactly how to perform calculations. Without access, opposing experts cannot see whether shortcuts, bugs, or biased assumptions exist.

Constructive Amendment vs. Variance

A constructive amendment changes the legal elements of the offense after grand-jury indictment—reversible per se. A variance is a minor mismatch (dates, wording) that does not alter elements; it is harmless unless it prejudices the defense.

CDR (Call Detail Records)

Telecom logs showing which cell tower a phone used during voice, text, or data events. Analysts map the tower sectors to estimate a device’s general location (often within 0.5–2 miles in urban areas).

5. Conclusion

United States v. Chavis sets a clear procedural marker: objections to the inner workings of forensic algorithms must be raised with specificity in the trial court or they are waived on appeal. While the Fourth Circuit did not substantively endorse TrueAllele, its refusal to entertain a belated source-code critique significantly strengthens prosecutors’ ability to rely on probabilistic DNA tools—at least where defense counsel remains silent until after conviction.

Beyond the expert-evidence point, the decision illustrates modern evidentiary synergy: digital footprints, surveillance video, analytics, and traditional witness testimony can collectively form an overwhelming circumstantial case. For defense lawyers, the message is two-fold: develop your technical record early and prepare to rebut the narrative woven from seemingly mundane digital artifacts. For courts, Chavis underscores both the continued vitality of Jackson’s deferential standard and the limited circumstances under which indictment variances warrant reversal.