The Effects of DNA Evidence on the Criminal Justice Process
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This research examines the effects of forensic deoxyribonucleic acid (DNA) evidence on decisions in the courts and on the conduct of criminal investigations. To assess effects on court decisions, quantitative analyses were conducted using primary data from the State of Queensland. A control-comparison method was used to assess the effects in court, and this was made within a context of other evidentiary and extra-legal factors that had a bearing on case outcomes. These other factors included defendant confessions, independent witness testimony and fingerprint and photographic evidence. A sample of 750 cases referred by police for prosecution and finalised past the appeal stage in court, was selected for examination. Half of these cases utilised DNA evidence, while the other half, as a control group, did not. Cases were selected in four categories: sexual offences, serious assaults, homicides and property crime. Data on the cases were analysed using advanced statistical methods and predictor models were developed to demonstrate how, given case configurations, the addition of DNA evidence could potentially alter court outcomes. Results for the three serious offence types were that DNA evidence emerged as a positive predictor that prosecutors would pursue cases in court, and it demonstrated a powerful influence on jury decisions to convict. Incriminating DNA evidence demonstrated no significant effect on inducing guilty pleas from defendants for serious crimes against the person. However, it did correlate significantly to cases reaching court and to guilty pleas being entered for property offence cases. The analysis of the effects on investigations relies on data from jurisdictions other than Queensland. Secondary data and the literature were used to assess the potential for strategically using forensic intelligence, along with dedicated investigative resources, to reduce property crimes like burglaries and car thefts. In the one study available that employed adequate research methods, three patrol areas in New South Wales, where a police operation was trialled, were compared to other areas that acted as a control. The police operation aimed at 100% attendance at property crime scenes, the use of intelligence from DNA and fingerprint identifications and specialised investigative resources to reduce crime levels. While the operation failed to achieve its goal, it did provide some valuable lessons. The effectiveness of the national criminal DNA database in the UK, reputed to lead the world, was then evaluated in relation to domestic burglaries. Its Australian CrimTrac counterpart did not commence operations until March 2003, and by 2004 was not operating at maximum capacity. Because no published studies were located that measured any effects of the UK database on crime levels, the criterion selected to measure performance was the proportion of convictions achieved through the database to reported crime. For domestic burglaries, this ratio was calculated from secondary official data to be close to one percent (0.01), a figure that included the additional convictions achieved through the intelligence that the database provided. The research also examined forensic DNA in relation to issues of privacy and civil liberties. Privacy issues are discussed beginning with an historical background to the use and misuse of genetic data. This includes the searches for a 'criminal gene' and for genetic links to criminal behaviour. DNA databases are contrasted with databanks, and it is questioned, since we leave our DNA wherever we go, whether it really is private. Civil liberties issues that are discussed include whether providing DNA is a form of self-incrimination; how DNA has helped exonerate the convicted innocent; wrongful convictions based on flawed DNA evidence; whether occasional 'mass screenings' with DNA are a reversal of the onus of proof; concerns with DNA databases and 'function creep', and the planting or 'forgery' of DNA evidence including the use of amplicon contamination. In the final chapter, a balance is sought between on one hand, the goal of police and government to provide a safe society, and on the other, the rights to privacy and civil liberties expected by individuals in Western liberal democracies. The chapter addresses the issues of concern raised in the earlier chapter about privacy and civil liberties, and makes recommendations on how these may be resolved. The general approach favoured is to increase police powers in specific situations, but to couple these with the protection of individual rights through greater regulation of those powers. The research also developed a case prioritising system aimed at helping clear laboratory backlogs.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Criminology and Criminal Justice
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