Every contact leaves a trace – a singular strand of hair or a tiny droplet of blood can be the silent witness at a crime scene. Locard’s Exchange Principle underpins all forensic science and holds that the perpetrator of a crime will bring something to the crime scene and leave with something from it.

Forensic experts use this principle daily to catch murderers and assailants. In Risking Life for Death, South African forensic pathologist Ryan Blumenthal offers a masterclass in this singular forensic technique based on real-life case studies. With more than 20 years’ experience in the field, Blumenthal explains how to look for clues and traces, and how what he does not find at autopsy is often more important than what he does find. In other words, the absence of evidence can sometimes be of greater value than the presence of evidence.

His account also highlights the dangers forensic pathologists are exposed to daily. As they try to unravel the puzzle of someone’s death, forensic pathologists often face life-threatening infections, toxic gasses and accidental injury, in effect risking their life for someone else’s death.

An understanding of Locard’s Exchange Principle can help you become a medical detective in your own life and can even help you be a happier person, Blumenthal argues.