CORRECT ERRORS UNVERIFIED 239 (43%) FAIL: ALL ARE INTERROGATED, 105 (44%) 3 (1%) 131 (55%) 105 (44%) CONFESS. 313 (57%) PASS: NONE ARE INTERROGATED, 18 (6%) ZERO 295 (94%) NONE CONFESS. TOTALS: 123 (22%) 3 (0.5%) 426 (77%) Mr. Murray does report three cases in which he discovered that he had made a false-positive error. These were cases in which there were two possible suspects; the first person tested had failed his test but Murray was suspicious of the result and broke his own rule by going on to test the other suspect. In each of the three cases, the second person tested also failed, was interrogated, and confessed. In one case, for example, the first suspect was an old lag, an habitual criminal whom Murray had happened to test on two previous occasions for other crimes. Both prior times, this man had failed, had been interrogated, and confessed. On this third occasion, he again failed the lie test but this time he continued to maintain his innocence. For this reason, Murray tested the other suspect, obtained a confession, and discovered that the habitual criminal was innocent of this third crime and that his third lie test had been in error. Murray concluded, however, that he had made only these 3 errors in 552 lie tests, an accuracy of 99.4%. It is important to see that Murray would have obtained much the same apparent confirmation if, instead of the polygraph, he had used for his lie test just the flip of a coin! About half of the coins would have come up 'heads' indicating deception (43% of them, if we use Murray's statistics.) About half of these purportedly deceptive subjects would have been guilty and many of the guilty ones, perhaps 105 of
CORRECT ERRORS UNVERIFIED 239 (43%) FAIL: ALL ARE INTERROGATED, 105 (44%) 3 (1%) 131 (55%) 105 (44%) CONFESS. 313 (57%) PASS: NONE ARE INTERROGATED, 18 (6%) ZERO 295 (94%) NONE CONFESS. TOTALS: 123 (22%) 3 (0.5%) 426 (77%) Mr. Murray does report three cases in which he discovered that he had made a false-positive error. These were cases in which there were two possible suspects; the first person tested had failed his test but Murray was suspicious of the result and broke his own rule by going on to test the other suspect. In each of the three cases, the second person tested also failed, was interrogated, and confessed. In one case, for example, the first suspect was an old lag, an habitual criminal whom Murray had happened to test on two previous occasions for other crimes. Both prior times, this man had failed, had been interrogated, and confessed. On this third occasion, he again failed the lie test but this time he continued to maintain his innocence. For this reason, Murray tested the other suspect, obtained a confession, and discovered that the habitual criminal was innocent of this third crime and that his third lie test had been in error. Murray concluded, however, that he had made only these 3 errors in 552 lie tests, an accuracy of 99.4%. It is important to see that Murray would have obtained much the same apparent confirmation if, instead of the polygraph, he had used for his lie test just the flip of a coin! About half of the coins would have come up 'heads' indicating deception (43% of them, if we use Murray's statistics.) About half of these purportedly deceptive subjects would have been guilty and many of the guilty ones, perhaps 105 of
2014_THE_LIE_DETECTOR_IS_BULL22411.docx