§ Mr. MullinTo ask the Secretary of State for the Home Department what use his Department makes of polygraphs, and if he will make a statement. [4585]
§ Mr. StrawNone, so far as I and my official have been able to ascertain. The Home Office does not encourage the use of polygraph testing for decision making on employment screening or security vetting. The Home Office's views on the use of polygraphs are broadly in accordance with those of the Scientific Affairs Board of the British Psychological Society. We have concern with regard to polygraphs' use of non-standardised administration procedures; internal inconsistency; unreliable rescoring of charts; insufficient evidence of retest reliability provided for examinees; disproportionate numbers of false positive results produced; absence of data on the adverse impact on minority groups; seemingly non-voluntary participation of examinees; and its sensitivity to aspects of temperament.
443W
§ Mr. MullinTo ask the Secretary of State for the Home Department what assessment he has made of the advantages of admitting in evidence the results of polygraph tests; and if he will make a statement. [4583]
§ Mr. MichaelI have made no assessment of the admissibility of polygraph tests as evidence in criminal trials. The courts have held that, as a matter of principle, evidence produced by mechanical, chemical or hypnotic truth test on a witness is inadmissible to show the veracity or otherwise of that witness.
Under the general rules of evidence, the previous statements of a witness are inadmissible as hearsay and also, where such statements are consistent with his oral testimony, they are inadmissible as evidence of consistency under the rule against previous self-serving statements.