Robbie Coltrane's Critical Evidence

When there's a murder with no suspect, no leads and perhaps not even a body, that's when investigators face their toughest test. Evidence must be gathered. Evidence must be analysed. But evidence is worthless if it can't be pinned to a suspect... Most murder victims knew the person that killed them. That's why homicide, in many cases, is a straightforward crime to solve. Yet 20% of UK homicides are classified as "circumstances unknown". In this series, Robbie Coltrane reveals eight of the harde…