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.

A young schoolboy is mysteriously shot in the head while playing in the school yard, but who fired the gun and from where? Philip Boyce, a forensic ballistics expert, is called in to test-fire a number of different guns and reconstruct the injuries to find out who fired the gun.

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.

After a 25-year-old woman goes missing in Bristol, the police launch a major missing-person enquiry. Soon after, the body of the young woman is discoved by dog walkers on Christmas Day, and the hunt becomes a major murder enquiry. As investigators can find no sign of forced entry to her flat, they conclude that her killer must be someone known to her.

This episode follows two shocking criminal cases in Yorkshire, each involving a woman murdered by her partner, and two expert witnesses with very different disciplines in forensic science who help to deliver justice.

In our first story, a community reels in total shock when a doting grandmother is found murdered in her home. Detectives search for the killer and suspect it may be someone close to her. The suspect's DNA is found all over the crime scene, but that is easily explained because he lived until recently in the same house. So the police try another route. They approach Kelly Sheridan, an expert witness in fibre evidence, who uncovers a trail of fibres, unravelling the mystery and putting the killer in jail.

An expert witness uses soil analysis to find the body of a missing woman feared murdered, and a cell site expert uses his tracking skills to catch a killer in Northern Ireland.

When a young nurse disappears, a soil analyst helps find her body and solve the crime. A digital imaging expert proves that what was thought to be an accidental death was murder.

An expert in microscopic lifeforms helps solve the murder of a teenager, and a handwriting expert assists an old lady whose house has been sold without consent.

A blood spatter analyst unlocks the mystery of a woman murdered in her own car, and an expert witness uses a mobile phone to help detectives solve a baffling murder case.

Police turn to a footprint analyst and a pollen expert to help solve a murder in Manchester, and a soil expert unearths the evidence needed to arrest a gang of treasure thieves.

Blood spatter analysis helps identify the killer of a body found in a suitcase, and an expert helps in a serious case of financial fraud that cost some victims their life savings.

An expert in mobile phone technology tracks the movements of a murder suspect, and an expert in art fraud determines whether a very expensive painting is genuine or fake.

A dental expert helps police investigating the mysterious death of a teenage girl, and an autograph expert is brought in to help convict scammers selling fake celebrity signatures.

When a man kills four people and goes on the run, a handwriting analyst is brought in, and after a body is found, an expert in pollen links the suspects to the scene of the crime.