On 20 April 2012, Brisbane real estate agent Gerard Baden-Clay reported that his wife Allison was missing. Ten days later, her body was found under a bridge more than 10 kilometres from the family home. Although the body was badly decomposed, there was no evidence that she had died of a natural cause. Before his trial on the charge of murder, Baden-Clay made application to the Supreme Court to exclude considerable expert opinion evidence relating to the injuries and the possible causes of death of his wife and what had appeared to have been recent scratches on his face. During the subsequent trial, the jury heard extensive evidence from a number of expert witnesses including a forensic pathologist, three forensic medical specialists, a forensic scientist, a botanist, an entomologist, a pharmacologist, a toxicologist and a general psychiatrist. On 15 July 2014, a jury convicted Baden-Clay of murder. On 8 December 2015, after considering the expert evidence and the trial judge's summing up to the jury, the Queensland Court of Appeal set aside the verdict as unreasonable and substituted a verdict of manslaughter. On 31 August 2016, the High Court overturned the decision of the Court of Appeal. The case commentary considers the application of the principles of law relating to the admissibility of expert opinion evidence and the directions a trial judge may give to a jury.