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Explaining reliability and validity of polygraph examinations is not a simple task, since many circumstances must be taken into account to conduct proper polygraph examinations.

One can only explain reliability and validity under the assumption that all the correct steps have been taken to maximize the reliability of the polygraph examination. A valid examination requires a combination of the properly trained examiner, a polygraph instrument that records as a minimum cardiovascular, respiratory, and electrodermal activity, and the proper administration of an accepted testing procedure and scoring system.

A multitude of studies have been conducted to discover the reliability of a polygraph examination. The consensus is in the fact that reliability is measured by the final verdict, meaning that if different polygraph examiners score the same charts they shoud arrive to the same result: Deceptive, Not Deceptive or Inconclusive.

Different entities have conducted studies on the reliability of polygraph examinations. The following represent some outcomes:

The American Polygraph Association has a compendium of research studies available on the validity and reliability of polygraph testing. The 80 research projects listed, published since 1980, involved 6,380 polygraph examinations or sets of charts from examinations. Researchers conducted 12 studies of the validity of field examinations, following 2, 174 field examinations, providing an average accuracy of 98%. Researchers conducted 11 studies involving the reliability of independent analyses of 1,609 sets of charts from field examinations confirmed by independent evidence, providing an average accuracy of 92%. Researchers conducted 41 studies involving the accuracy of 1,787 laboratory simulations of polygraph examinations, producing an average accuracy of 80%. Researchers conducted 16 studies involving the reliability of independent analyses of 810 sets of charts from laboratory simulations producing an average accuracy of 81%.

The validity of the polygraph examination depends basically on agreements between prosecution and defense or by rulement of judges.

In Europe, not many attemps have been made to introduce polygraph examinations into European courts, so there is a popular perception in society thinking that polygraph examinations are not valid in courts. This is true until the first qualified attempt is accepted by justice. Unfortunately, the lack of trained Polygraph Examiners in Europe and the misconception of polygraph examinations by defense lawyers have not yet allowed a real debate about this instrument that is a vital tool to improve judgments and increase safety of the society.

The admissability of polygraph in courts

Polygraph results (or psychophysiological detection of deception examinations) are admissible in some federal circuits and some states. More often, such evidence is admissible where the parties have agreed to their admissibility before the examination is given, under terms of a stipulation.

Some jurisdictions have absolute bans on admissibility of polygraph results as evidence and even the suggestion that a polygraph examination is involved is sufficient to cause a retrial.

The United States Supreme Court has yet to rule on the issue of admissibility, so the rules in federal circuits vary considerably. The Supreme Court has said, in passing, that polygraph examinations raise the issue of Fifth Amendment protection, [Schmerber v. California, 86 S. Ct. 1826 (l966).] The Supreme Court has also held that a Miranda warning before a polygraph examination is sufficient to allow admissibility of a confession that follows an examination, [Wyrick v. Fields, 103 S. Ct. 394 (1982).] In 1993, the Supreme Court removed the restrictive requirements of the 1923 Frye decision on scientific evidence and said Rule 702 requirements were sufficient, [Daubert v. Mettell Dow Pharmaceutcals, 113 S.ct. 2786.]Daubert did not involve lie detection, per se, as an issue, as Frye did, but it had a profound effect on admissibility of polygraph results as evidence, when proffered by the defendants under the principles embodied in the Federal Rules of Evidence expressed in Daubert, see [United States v. Posado (5th Cir. 1995) WL 368417.]

Some circuits already have specific rules for admissibility, such as the 11th Circuit which specifies what must be done for polygraph results to be admitted over objection, or under stipulation, [United States v. Piccinonna 885 F.2d 1529 (11th Cir. 1989).] Other circuits have left the decision to the discretion of the trial judge. The rules that states and federal circuits generally follow in stipulated admissibility were established in [State v. Valdez, 371 P.2d 894 (Arizona, 1962).] The rules followed when polygraph results are admitted over objection of opposing counsel usually cite [State v. Dorsey, 539 P.2d 204 (New Mexico, 1975).] Primarily because of Daubert, as well as the impact the other cited cases have had, polygraph examination admissibility is changing in many states. Many appeals, based on the exclusion of polygraph evidence at trial are now under review by appellate courts.

 

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