Posado and the Polygraph: The TruthBehind Post-Daubert Deception Detection

I. Introduction Society views the law as a means of seeking truth and dispensing justice.1 The issue of witness credibility lies at the heart of this search.2 The law constantly seeks accurate methods of measuring witness credibility by either verifying truthfulness or detecting deception.3 The most important scientific technique for assessing a witness's credibility is the polygraph test.4 Nevertheless, courts have been extremely reluctant to embrace the use of polygraph evidence.5 This Note analyzes the role of polygraph evidence in federal criminal cases. Part II provides a brief introduction to the Federal Rules of Evidence governing admissibility of polygraph evidence.6 Part III describes the different tests used to determine the admissibility of scientific evidence with special emphasis on Daubert v. Merrell Dow Pharmaceuticals, the most recent Supreme Court decision in the area.7 Part III.A focuses on the Fifth Circuit's interpretation of Daubert as the case relates to polygraph evidence in United States v. Posado.8 Posado is a revolutionary decision which concludes that a per se ban on polygraph evidence is untenable after Daubert. Further, Posado articulates a three-step inquiry applicable to all cases in which there is an issue of polygraph evidence admissibility. The tripartite inquiry is not a monumental departure in the area of polygraph admissibility, but the Fifth Circuit's analysis is remarkably broad. Part III.B discusses how other United States Circuit Courts of Appeals responded to Daubert and how their responses differed from the Fifth Circuit's approach.9 Part III.C analyzes the impact of the decision and examines how district courts in the Fifth Circuit have applied Posado.10 Part IV describes the three primary arguments against admitting polygraph evidence: (1) that the polygraph is unreliable, (2) that the evidence has an undue impact on the jury, and (3) that defendants can manipulate results by using a friendly polygrapher. Part IV concludes that empirical analysis does not support any of these contentions.11 Part V articulates a constitutional argument based on Due Process Clause and Confrontation Clause principles for admitting exculpatory polygraph evidence.12 Part VI then analyzes the admissibility of polygraph evidence generally in criminal cases under the applicable Federal Rules of Evidence.13 Finally, Part VII of this Note offers a pragmatic solution to the problem of when to admit polygraph evidence. 14 II. The Applicable Federal Rules of Evidence The admissibility of polygraph evidence implicates numerous Federal Rules of Evidence, including Rules 104(a), 401, 402, 403, 608(a), 702, and 703. Rule 104(a) states that a court shall make all determinations regarding the admissibility of evidence.15 Rule 401 governs the relevance of evidence and defines relevant evidence as any evidence tending to make the existence of any consequential fact more or less probable.16 Rule 402 complements Rule 401 by stating that relevant evidence generally is admissible.17 Rule 403 also governs relevance and notes that if the danger of unfair prejudice substantially outweighs the probative value of the evidence, then the court may exclude the evidence.18 Rule 608(a) states that evidence of truthful character is admissible only after a party has attacked a witness's character for truthfulness.19 Rule 608(a) is important because it provides an evidentiary theory as to how courts may admit polygraph evidence generally.20 Rules 702 and 703 provide an alternative basis for polygraph admissibility.21 Rule 702 provides that if scientific knowledge will assist the trier of fact in determining a fact at issue, then a witness qualified as an expert may give an opinion based on his or her specialized knowledge.22 Rule 703 provides that so long as the inferences that provide the basis for the expert's opinion are of a type upon which other experts reasonably rely, then the facts or data underlying the theory need not be admissible. …