Improper Use of Forensic Science | Expert Witnesses

Improper Use of Forensic Science or Expert Witnesses occurs when a prosecutor knowingly, recklessly, or negligently presents false, unreliable, or misleading scientific evidence or expert testimony, or when they fail to disclose weaknesses, limitations, or exculpatory findings. This misconduct undermines the reliability of the fact-finding process and may result in wrongful convictions.

Scope:

  • Presentation of Unreliable Science: Using unvalidated or discredited forensic methods (e.g., bite-mark analysis, flawed hair microscopy).

  • Unqualified or Biased Experts: Calling witnesses without proper credentials, or experts with undisclosed conflicts of interest.

  • Mischaracterization of Results: Exaggerating certainty, overstating probabilities, or presenting inconclusive results as definitive proof.

  • Suppression of Scientific Reports: Withholding or delaying disclosure of exculpatory lab results, peer reviews, or known error rates.

  • Failure to Correct False Testimony: Allowing expert witnesses to misstate findings without correction.

Examples:

  • Presenting a forensic analyst’s testimony claiming “100% certainty” of a match when the methodology has an acknowledged error rate.

  • Using a medical examiner who lacks forensic pathology certification to testify beyond their expertise.

  • Failing to disclose that a DNA test excluded the defendant, while presenting other inconclusive test results.

Related Standards:

  • Brady v. Maryland, 373 U.S. 83 (1963): Requires disclosure of exculpatory scientific evidence.

  • Giglio v. United States, 405 U.S. 150 (1972): Requires disclosure of impeachment evidence, including expert credibility issues.

  • Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993): Establishes judicial gatekeeping for scientific testimony.

  • ABA Model Rule 3.3 & 3.8: Prohibit prosecutors from presenting false evidence and require disclosure of evidence negating guilt.

Consequences:
Improper use of forensic science or expert witnesses can result in wrongful convictions, reversal of verdicts, suppression of testimony, professional sanctions, and long-term damage to public trust in the justice system.