Some criminal investigations are so complicated that they require a number of expert witnesses to be involved. This programme examines how forensic evidence from a whole team of scientists turned a missing-person case into a hunt for a murderer, and then into an investigation into one of Britain's most notorious serial killers.

After the body of a young Polish woman was discovered in the basement of a church in Glasgow, police observed an element of organisation and methodology behind the killing and became convinced the culprit had murdered before. They launched a huge operation to dig into the killer's life: where he had been living, what he had been doing, and which nearby crimes remained unsolved? Their investigation led them to two cold cases, but only evidence from expert witnesses could reveal if these were the work of the same killer. The police enlisted the help of forensic scientists Jennifer Miller, Carol Rodgers and Peter Faulding - experts in a range of different disciplines, from bioarchaeology to forensic biology and ground-penetrating radar testing - to help them gather evidence. And despite the passage of time, the experts ensured that no piece of evidence was overlooked and that the truth was finally discovered.

Following the unexplained death of a man in Yorkshire, found alone in his home with no signs of forced entry or a struggle, police were at a loss to explain his death. They turned to expert witness Duncan Campbell to help solve the mystery. Duncan, a forensic scientist, decided to analyse something that is part of everyday life, food. After examining the man's final meal, the expert witness not only solved the crime, but in turn helped to make legal history by ensuring a guilty verdict was achieved in this very rare and unusual case.

Sometimes, before a murderer can be identified, the victim must be identified. Such a challenge faced the police when human remains washed up on a beach in Scotland. Detectives enlisted the help of expert witness Caroline Wilkinson to identify the body of the unknown victim. An expert in forensic facial reconstruction, Caroline was able to rebuild the facial features of the young woman. This allowed police to identify the victim and in turn enabled them to catch her killers and put them behind bars.