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PhD ThesisThe aims of the present research were two-fold: firstly, to investigate the utility of
post-conviction polygraphy with community-based sex offenders; and secondly, to
examine the accuracy of the polygraph in this context. The initial study examined
whether periodic polygraph testing acted as a deterrent for engaging in risk
behaviour. Fifty adult male sex offenders taking part in community treatment
programs were allocated into 2 groups: "Polygraph Aware" subjects were told they
would receive a polygraph examination in 3 months regarding their high-risk
behaviours, while "Polygraph Unaware" subjects were told their behaviour would
be reviewed in 3 months. Relevant behaviours for each subject were established at
baseline interviews, following which both groups were polygraphed at 3 months.
All subjects were polygraphed again at 6 months. Thirty-two subjects (64%)
attended the first polygraph examination, with 31 (97%) disclosing an average of
2.45 high-risk behaviours each previously unknown to supervising probation
officers. There was no significant difference between the two groups. Twenty-one
subjects (42%) completed the second polygraph test, with 71% disclosing an
average of 1.57 behaviours, a significant decrease compared with the first test.
Disclosures to treatment providers and probation officers also increased.
Polygraph testing resulted in offenders engaging in less high-risk behaviour,
although the possibility that offenders fabricated reports of high-risk behaviours to
satisfy examiners is also considered; similarly offenders seemed to be more honest
with their supervisors, but this only occurred after the experience of the test itself.
The second study examined the accuracy of the polygraph as used in a postconviction
context with sex offenders. One hundred and seventy-six sex offenders
engaged in treatment and required to complete biannual polygraph tests focussed
upon offending and other risk behaviours. The participant's regular polygraph
maintenance test was used for the study, however, in addition to the regular issues
covered in this test the examiner included `drug use' over the preceding three
months as a relevant question. Immediately after the polygraph test a hair
specimen was collected and subsequently analysed for drugs. The polygraph was
reasonably accurate with identifying truth telling (79%), while 21% were wrongly
accused of drug use. Only a small number of offenders (n = 5) were found to be
taking drugs and lying about having done so. The blind scorers correctly identified
all of these individuals (100%). The Area under the curve index was .
88. The
inter-rater reliability between the blind scorers and the original examiners was
poor. The original examiners were less accurate than the blind scorers (Area under
the curve index = .
68) and only correctly identified two of the five liars (40%).
False positives were associated with lower intelligence and having experienced a
sanction due to a polygraph result. False negatives were not associated with
demographic characteristics, personality variables or intelligence. The majority of
offenders found the polygraph to be helpful in both treatment and supervision.
Nine per cent of offenders claimed to have made false disclosures; these
individuals -had higher scores on ratings of Neuroticism and lower scores on
ratings of Conscientiousness. The implications of these results are discussed.
Overall, the findings support the view that the polygraph is both useful and
accurate in the treatment and supervision of sex offenders
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