Murder or manslaughter: the role of premeditation and associated behavioural characteristics

Abstract

Behavioural differences between murder and manslaughter have rarely been empirically assessed. By examining real-world data, assessment of this type helps ensure that the legal classification and sentencing framework aligns with the nuances of criminal behaviour and contributes to just outcomes. Additionally, empirical assessment of differences between offence types provides an inclusionary/exclusionary basis in the pooling of samples. This study examined the relationships between demographic and crime-scene behaviours with conviction outcome (i.e. either murder or manslaughter) in 253 New Zealand homicides. Premeditated intent to kill was highly associated with murder as the conviction outcome; however, lower levels of premeditation were not. Other significant predictors were primarily those of a mitigating nature; a victim provoking an attacker or an offender attempting to save the victim were observed to potentially reduce the likelihood of a murder conviction, while aggravating factors such as the use of a weapon increased this likelihood. Most variables did not significantly predict conviction outcome for either homicide type, indicating these types of crimes are perhaps more similar than they are different. Overall, this study helped reveal an intricate interplay of factors which impact on homicide conviction outcomes, shedding light on the decision-making process within the criminal justice system.