The validation of the polygraph examination in forensic psychiatry

An interesting historic abstract to attempt to establish the validity of the use of polygraph techniques when establishing insanity.  Polygraphs are not admissible as evidence in UK courts as to their unreliability and highly questionable validity however they are used in many places including areas of the US.  Is there any reliable method of determining insanity – Szasz, Laing and Rosenhan would  argue categorically not?  But is there any evidence to support the polygraph as a method.  In this fundamentally flawed piece of research there is an attempt to provide concurrent validity to support the use of a Polygraph.  Access the full site here.

 Introduction

There is increasing demand for psychiatric expert testimony in criminal proceedings. A person is responsible for his actions unless he is subject to the penal code, Section 34 h, insanity. Mental illness is not sufficient to determine insanity; it must be proven that the patient did not understand what he had done, did not comprehend the inappropriateness of his actions: or could not have avoided performing the deed. Opponents argue that the expert testimony is not scientific and not professional and alternatively that the mentally ill avoid responsibility even when there is no connection between the illness and the offence.

Objectives

The polygraph examination is an important instrument for confirming credibility of the testimony but it has not yet been investigated in the field of forensic psychiatry.

Aims

To examine the validity of a polygraph examination in psychotic patients. To compare polygraph tests with psychiatric examinations.

Methods

Patients were tested with a polygraph examination on there misjudged psychotic behaviour.

Results

24 patients signed a consent form, but not all eventually participated. All patients received anti-psychotic medications. In general valid polygraph examination can be performed to patients with the psychotic illnesses (i.e. schizophrenia). Agitated or cognitive deprived patients tests were not reliable. The psychiatric examinations or the expert testimonies were in accord with the polygraph examination.

Conclusions

Preliminary data indicate that polygraph examinations are valid in patients with the psychotic illnesses. But not in agitated or cognitive deprived patients. Expert testimonies were found reliable in determining insanity.