Dr Sheila Willis is a forensic scientist who was Director General of Forensic Science Ireland for many years. She has spent her life using science to help solve cases, working on crime scenes and then analysing material in the lab, and presenting scientific evidence in court. It’s a complicated business. Forensic science relies on powerful technology, such as DNA analysis, but it cannot be that alone - it’s also about human judgement, logical reasoning and asking the right questions. It is these fundamentals of forensic science that Sheila has fought for through her long career and what she fears may be becoming lost from the field now. We find out what happens when the two very different worlds of science and the law clash in the courtroom. How to walk the line of presenting scientific evidence where there is pressure to be definitive where often science cannot be - and what this part of the job has in common with food packaging. And what makes a good forensic scientist? We’ll turn the studio at London’s Broadcasting House into a live crime scene to see if host Professor Jim Al-Khalili would be any good as a forensic investigator… Produced by Gerry Holt