Sue Black, the UK's leading forensic scientist, has forty years' experience analysing criminal case evidence. And acting as an expert witness, over the same period she has repeatedly put her research and reputation on the line, all in the name of justice.

Now in An Expert Witness she puts forensic science itself on trial. From nineteenth-century poisonings to modern sex crimes, the first identification techniques to the possibilities provided by artificial intelligence, Sue traces the evolution of forensics. She shows how the scientist sits in a fraught but critical relationship with both our law enforcers and the Law. And she reminds us that while there have been huge leaps forward - the discovery of DNA fingerprinting, Sue's own vein identification research - there are also cases like Andrew Malkinson, wrongly convicted and imprisoned for seventeen years, which demonstrate the horror when mistakes are made.

In the third book of a trilogy that includes All That Remains and Written in Bone, Sue uses shocking landmark cases to tell the story of forensic science: In which cases did justice prevail? Why do things go wrong? What should we fight to preserve? And why does this book mark the end to a key part of her extraordinary career.