The post-conviction polygraph in forensic practice

Field: Psychology (Social Sciences)

The aim of this thesis is to examine the impact of polygraphy disclosure and recidivism (particularly for sex offenders), gain greater understanding of some of the psychological mechanisms involved, and, in the light of this, consider the value of its application in forensic settings. Chapter one presents a general introduction to the topic. Chapter two presents a systematic review of the relevant literature. In particular, it explores the utility of postconviction polygraph testing amongst sexual offenders, with a primary focus upon its influence in facilitating disclosure. The findings are generally supportive of the view that the polygraph is a useful technique for eliciting additional information from offenders, which, in turn, can assist in achieving a more accurate understanding of current risk and criminal history. It is noted, however, that there continues to be a paucity of high quality research evidence, in particular, a lack of adequately controlled studies. Further research is needed to gain more secure understandings of the polygraph’s potential. Chapter three offers a critique of the use of the postconviction polygraph in the monitoring, assessment and supervision of convicted sex offenders. This notes a degree of partisanship in arguments for and against its use. The chapter seeks to offer an analysis of available evidence concerning the utility of the post-conviction polygraph in encouraging disclosures amongst sexual offenders under investigation in both custodial and noncustodial settings. Those who support the use of the polygraph typically argue that such disclosure provides fuller histories of deviant sexual behaviour, admissions of previously unknown offences/victims, and increased reporting of other high-risk behaviours. However, noting the concerns of those opposed to its use, the ongoing challenges and shortfalls of the polygraph are also referenced. In the light of the analysis, it is proposed that the method should not be used in isolation but, where appropriate, in conjunction with a range of other assessment tools before reaching a risk-related conclusion concerning sexual offenders. The ‘bogus pipeline to the truth’ effect is an argument used to challenge the veracity of polygraph data, as its underlying premise is that the value of the polygraph in eliciting disclosure is not grounded in its accuracy, but, rather, in false claims regarding its ability to detect deception (which, as a result, will often elicit more truthful responses from those being tested). In other words, disclosure can be derived from psychologically manipulating examinees by convincing them that the lie detector is significantly more accurate than it actually is. In chapter four, an empirical research study explores the bogus pipeline effect upon disclosures made by students who were earlier exposed to cheating behaviour. Participants experienced within-group cheating by a study confederate and later placed in one of three conditions in which they were asked about the occurrence of cheating within their group. Two groups were attached to a bogus lie detector and informed that this was either 75% accurate or 100% accurate. Control participants were not attached to the lie detector, but simply asked if they had been present in a group that had cheated. Findings demonstrated that those participants attached to a bogus lie detector were more likely to disclose cheating within their group than those asked in the absence of the machine. However, there were no significant differences in rates of disclosure between the 75% and 100% condition. The influence of suggestibility, personality and gender upon disclosure amongst all conditions revealed no effects confounding the relationship. A single case study is presented in Chapter five. It details some of the ways by which the psychologist can encourage a client with paranoid schizophrenia, and a history of sex offending, to reflect openly upon his psychological and behavioural circumstances. Subsequently, it considers whether a measure such as the polygraph, designed to encourage honest accounts and attributions, could be of value in work with those clients whose thought processes are distorted by psychotic conditions. In contextualising this issue, the chapter describes and evaluates the usefulness of a ten week psychosis awareness group programme for a sexual offender treated within a medium security hospital. The influence of this psychoeducation programme on levels of understanding, disclosure and personal acceptance of his mental illness is discussed, and recommendations for further psychological work are made. Subsequently, the association between psychotic symptoms and sexual offending is explored, as is the suitability of a future polygraph for this client In Chapter six a synoptic discussion of the work presented concludes the thesis. This addresses the current position on the bogus pipeline paradigm. Finally, the chapter seeks to provide an informed position concerning the use of the post-conviction polygraph in forensic settings.