United States v. Danilo Garcia, 752 F.3d 382

Garcia, one of fourteen defendants, was convicted on five counts of heroin trafficking after severance from co-defendants.
The Government relied largely on surveillance evidence and wiretap calls with a decoded-language expert, Agent Dayton.
Dayton testified as both decoding expert and, at times, a fact witness, leading to concerns about dual roles and foundation.
The district court allowed Dayton’s testimony despite defense objections about methodology and basis for interpretations.
Garcia moved for judgment of acquittal on one count; the district court denied, and the jury convicted on five counts.
This court vacates and remands, finding the decoding expert testimony infected the entire trial with prejudice.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether decoding expert testimony was admissible and properly grounded	Garcia contends Dayton’s testimony lacked reliable foundation	Government maintains proper expert qualifications and methodology	Abuse of discretion; admissibility not cured by safeguards; vacate for prejudice
Whether safeguards mitigated jury confusion between expert and fact testimony	Dayton’s dual role risked jury confusion	Any confusion was mitigated by court instructions	Safeguards insufficient; dual-role prejudice remained; require remand
Whether the foundation and reliability of Dayton’s interpretations were adequate	Foundations for many interpretations were missing	Methodology explained and applied in many instances	Record shows inadequate foundation; not reliably applied across interpretations; remand warranted
Whether the error was harmless given other evidence	There was insufficient non-Dayton evidence to sustain convictions	Evidence apart from Dayton supported convictions	Error not harmless; convictions vacated for prejudice
Whether the district court’s handling of Rule 702/16 disclosures affected the outcome	Disclosure and gatekeeping were deficient	Court properly admitted witness under hybrid testimony framework	Court abused gatekeeping; remand necessary

United States v. Wilson, 484 F.3d 267 (4th Cir. 2007) (evaluate decoding expert testimony; abuse of discretion standard)
United States v. Baptiste, 596 F.3d 214 (4th Cir. 2010) (dual-role expert/fact witness safeguards and Johnson language)
United States v. Johnson, 587 F.3d 625 (4th Cir. 2010) (concerns about relying on cooperating witnesses for expert opinions; Crawford concerns)
United States v. Banks, 482 F.3d 733 (4th Cir. 2007) (harmful impact of erroneous admissibility rulings when evidence is not overwhelming)
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (S. Ct. 1999) (Daubert framework for reliability of expert testimony)