MERCY killings are seen as less serious than murders of self-defence, and a burglar who kills a woman in panic is viewed more harshly than someone who murders a battering spouse, according to a recent study. Barry Mitchell, reader in criminal justice at Coventry University, presented 822 members of the public with eight hypothetical homicide scenarios, asking them to rate them on a scale of severity from one to 20. The study, Public perceptions of homicide and criminal justice, also found people were critical of those who failed to intervene to stop a killing.