Professor David Wilson, the UK's leading criminologist, presents the third series of Crime Files, this time, focusing on cold cases. In episode 2, he discusses mysterious deaths and how the circumstances surrounding them can lead to decades old unsolved cases which remain unanswered to this day.David visits Boarhills in Fife to investigate the death of former soldier Sandy Drummond. Sandy was thought to have died of natural causes because of the absence of visible injuries but following a post mortem it was determined he was murdered by a martial arts move on his neck.Crime writer Douglas Skelton talks to David about the unusual behaviour displayed by Sandy in the days leading up to his death and how his mother Effie died without ever finding out the answers she was searching for.David, this series, is joined in studio by our resident Forensic Scientist Helen Meadows. Helen will dissect the evidence which surrounded Sandy Drummond's case and will also inform David of the curious death of Robert Higgins from Kirkliston near Edinburgh.David travels to Kirkliston to examine the last weekend of Robert Higgins, who was murdered in 1995. Robert, who was usually a creature of habit spent his last days away from family and friends in the presence of a mystery couple. Crime reporter Jane Hamilton covered the case at the time and speaks to David about the unusual location where Robert Higgins was discovered as well as the questions still left behind by the mysterious murder.