With so many forensic techniques available, detectives and expert witnesses can sometimes disagree on how best to search for evidence. In 2006, a team investigating three notorious cold cases in Pembrokeshire were convinced DNA analyses would hold the answers. But when that drew a blank, they had to rethink their approach entirely. What followed was the forensic equivalent of a trail of breadcrumbs that eventually led to the killer.

Expert witnesses help solve all types of crime, not just violent ones. Our next case is an unusual case of fraud. It involved diamonds and expensive wine, and cost some victims their entire life savings. The fraudster might have got away with it, but an expert witness with a very unusual specialism was finally able to reveal the evidence that secured a prosecution. We go to a diamond lab in Birmingham to investigate how gemstone expert Richard Taylor uncovered the fatal flaw in this devastating diamond investment scam. Show less