The cases that stunned Australia - and left us all with one question: why did they do it? Gerard Baden - Clay was described as charming and successful, with a picture - perfect life, until he murdered his wife, Allison. John Myles Sharpe killed his pregnant wife and their young daughter with a spear gun. Simon Gittany flung his fiancée off the balcony of his upmarket inner - city apartment, having proposed lovingly to her, in public, just two months before. These and other crimes, committed by people described as average, ordinary, normal...In Why Did They Do It?, respected journalist Cheryl Critchley teams with esteemed psychologist Dr Helen McGrath to dissect the cases and identify the personality disorders of each of the killers. Using psychological analysis, combined with scientific evidence, they identify the reasoning and motives of the men and women whose brutal crimes shocked the nation.