The Effects of DNA Evidence on Homicide Cases in Court

Abstract

This study examines the effects that deoxyribonucleic acid (DNA) evidence had on decisions in homicide cases as they progressed through the criminal courts. These effects were examined within a context of other evidentiary and extra-legal factors that may also have had a bearing on case outcomes. A sample of 150 solved and completed cases referred by police for prosecution in the jurisdiction of Queensland was selected for examination. In half of these cases prosecutors produced DNA evidence to relate the accused to the crime, while the other half acted as a control group and did not include DNA evidence. Outcomes of the analyses were that cases with DNA evidence were much more likely to reach court than cases without, while incriminating DNA evidence demonstrated a powerful influence on juries' decisions to convict. Additionally, some extra-legal social factors such as age and gender of defendants or victims proved to be predictors of court outcomes at various stages. DNA was associated with a slightly decreased length of imprisonment for manslaughter offences. As with previous controlcomparison studies on sexual offences and serious assault cases, in homicide cases DNA evidence demonstrated no significant statistical relationship with guilty pleas.