한국의 검찰에서는 거짓말탐지검사(polygraph test)의 최종판정을 위한 기준 점수로써 관행적으로 -12점을 사용하고 있다. 이 판정기준 점수는 검사기법을 개발한 Backster(1963)가 제안한 판정기준 점수(-13점)와는 약간 다른 것으로 한국에서 거짓말탐지 검사를 표준화하기 위해서는 판정기준 점수에 대한 과학적 근거와 그 정확성에 대한 검증이 필요하다. 본 연구에서는 실제 범죄수사를 위하여 검찰에서 이루어진 거짓말탐지 검사 자료를 이용해서 거짓말탐지 검사의 판정기준 점수를 신호탐지이론에 기초하여 설정하고자 하였다. 또한 Backster가 제안한 판정기준 점수와 현재 검찰에서 사용하는 판정기준 점수, 신호탐지이론에 기초해서 본 연구가 설정한 판정기준 점수의 정확성을 비교하여 범죄수사를 위한 거짓말탐지검사의 검사 상황에 가장 적절한 판정기준 점수를 제시하고자 하였다. 신호탐지이론에 기초해서 거짓말탐지검사의 정확성을 최대화할 수 있는 판정기준 점수를 산출한 결과 -8점으로 나타났다. 또한 판정기준 점수를 도출한 표본자료와 다른 별도의 표본자료에서 판정기준 점수에 따른 정확성을 비교한 결과, -8점을 판정기준 점수로 사용했을 경우의 정확성(83.17%)이 가장 높았고, 검찰의 판정기준 점수(80.20%), Backster의 판정기준 점수(76.24%) 순으로 정확성이 감소하였다. 그러나 오류긍정과 오류부정의 비율을 비교한 결과에서는 -8점을 판정기준으로 사용할 때에 오류긍정이 가장 높은 것으로 나타났다. 따라서 범죄수사를 위한 거짓말탐지검사에서 전체적인 판단 정확률을 확보하는 것이 중요하다면 -8점을 기준 점수로 사용하고, 진실을 말하는 사람을 거짓이라고 판단하지 않는 것이 중요하다면 -12 또는 -13점을 판정기준 점수로 사용할 것이 권고 되었다.
The polygraph test administered by the Korean Prosecutors Office for crime investigations customarily uses the score of -12 as the cutoff point separating the subjects who lie from those who tell the truth. The criterion used by the KPO is different from the one (-13) suggested by Backster (1963) who invented the particular method for lie detection. Based on the signal detection theory applied to the real polygraph test data obtained from real crime suspects by the KPO, the present study identified the score of -8 as an optimal criterion resulting in the highest overall accuracy of the polygraph test. The classification of the subjects with the score of -8 as the criterion resulted in the highest accuracy (83.17%) compared with the accuracies of classifications with the Backster's criterion (76.24%) and the KPO's criterion (80.20%). However, the new criterion was also found to result in more false-positive cases. Based on the results from the present study, it was recommended to use the score of -8 as the criterion when the overall accuracy is important but the score of -12 or -13 when avoiding false-positive is more important than securing the overall accuracy.
대검찰청, (2008) 2007년 종합 심사 분석, 대검찰청
엄진섭 ; 지형기 ; 박광배, 폴리그라프 검사의 정확도 추정, 한국심리학회지: 사회문제
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