When fire crews attended a blaze at a hostel in West Sussex, they quickly discovered a burned body on a bedroom floor. It belonged to 37-year-old mother of five Melanie Grey and it was clear she'd been the victim of a brutal attack. As they launched a murder investigation, police needed to know what had happened in the victim's final moments, so they called on a blood spatter analyst. Because of fire damage, carrying out a forensic investigation of the crime scene was going to be extremely challenging. Confident the blood staining under the fire residue would tell an important story, expert witness Jo Millington used an innovative technique to remove the soot and uncover the truth. Melanie's sons Sam and Zeth Ockenden recall the night of the murder and the devastation of losing their mother. Forensic science is developing all the time, meaning there may well be no case that cannot eventually be solved. In 1973 a 16-year-old girl was sexually assaulted and killed on her way home after a night out. Months later, two more teenage girls died when they became victims of a savage attack in what became known as the Steeltown murders. Police believed the same killer could be responsible for all three girls' deaths, and a huge investigation was launched. However, no suspects were identified, and it would take until the late 1990s, when the cases were reinvestigated, for a suspect to finally be named. A pioneering DNA analyst, Dr Colin Dark, carried out the world's first use of familial DNA tracing to posthumously identify a serial killer and to solve a previously unsolved murder. With revealing interviews from Dr Dark and detective Paul Bethell.