United States v. Clacy Herrera, 704 F.3d 480

District judge excluded the two latent fingerprints from the heroin evidence due to alleged chain-of-custody flaws; mandamus ordered admission of the exhibit and related testimony.
Evidence had been supported by ten government witnesses; the mandamus proceeding interrupted the trial and led to reassignment to a different district judge.
After reassignment, the new judge allowed the fingerprint evidence and the trial proceeded to a conviction on multiple drug-related counts.
The government’s latent print match used ACE-V methodology to relate latent prints to defendant’s patent prints; defendant challenged reliability under Daubert/Kumho framework.
The appellate panel held the mandamus was warranted to correct a baseless, prejudicial ruling, and that the fingerprint evidence should have been admitted; issues about jury reassignment were meritless.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility of latent fingerprint evidence under 702/Daubert	ACE-V is reliable; latent-to-patent match admissible.	Fingerprint matching is insufficiently reliable to admit as scientific evidence.	Fingerprint evidence admissible; ACE-V reliability supported; admissibility remains subject to trial challenges.
Whether mandamus correction was appropriate for the district court's ruling	The district ruling was seriously defective and prejudicial.	Mandamus overreach would suppress prosecution.	Mandamus correction warranted; ruling could not stand.
Impact of reassignment on trial fairness	Reassignment prejudiced defendant by influencing jurors.	New judge's conduct biased the jury against defendant.	No reversible prejudice; reassignment did not undermine fairness.
Effect of new judge's instructions during deliberations	Instructions pressured jurors to hurry.	Deliberations were rushed due to scheduling pressures.	No coercive pressure; jurors acted independently in deliberations.

Will v. United States, 389 U.S. 90 (1967) (mandamus not substitute for forbidden appeal; limits on government appeals)
Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (Supreme Court, 1993) (rule of reliability for scientific evidence under Rule 702)
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (Supreme Court, 1999) (non-scientific expert testimony governed by Daubert-like standards)
Perry v. New Hampshire, 132 S. Ct. 716 (U.S. Supreme Court, 2012) (limits on eyewitness reliability and jury considerations)
United States v. Lee, 502 F.3d 691 (7th Cir. 2007) (chain of custody and admissibility framework for forensic evidence)
United States v. Ford, 683 F.3d 761 (7th Cir. 2012) (DNA analogy for probabilistic reasoning in forensic evidence)
United States v. Vinyard, 539 F.3d 589 (7th Cir. 2008) (mandamus power to correct district court errors)