Chainalysis's Reactor Software Used in Bitcoin Fog Trial as Valid Court Evidence

Introduction

The September 25 ruling upheld Roman Sterlingov’s convictions after he failed to explain why Reactor’s source code was material to his defense. The Bitcoin Fog appeal upheld expert testimony based on proprietary wallet tracing, with explained methods and corroboration supporting its admission.

Background

Blockchain analysis company Chainalysis drew attention to that result in October 13 commentary, presenting it as further validation of its Reactor software. The judgment itself came on September 25, when the D.C. Circuit affirmed Sterlingov’s convictions and 150-month sentence for operating Bitcoin Fog, a service that mixed users’ bitcoin to obscure transaction trails.

Expert Testimony and Reliability

Under Federal Rule of Evidence 702, the party offering a qualified expert must demonstrate, more likely than not, that the testimony will help the fact-finder, rests on sufficient facts or data, uses reliable principles and methods, and reflects a reliable application of those methods to the case. Daubert supplies considerations for that reliability inquiry, including testing, peer review, known or potential error rates, and general acceptance.

Attribution and Error Rates

The appeals court explained that these considerations are flexible and nonexhaustive. The appellate posture also matters. The panel reviewed admission of the testimony for abuse of discretion, recognizing the trial judge’s latitude both in deciding how to assess reliability and in reaching a reliability determination. FBI witness Luke Scholl and Chainalysis analyst Elizabeth Bisbee testified that Reactor clustered and attributed more than 900,000 Bitcoin addresses to Bitcoin Fog.

Conclusion

The DC Circuit’s decision matters because it explains how proprietary analysis became usable courtroom evidence and why this particular disclosure challenge failed. Its reasoning keeps three questions separate: whether expert testimony is reliable enough to admit, whether addresses have been attributed correctly, and what that evidence establishes about a person.