Just one drop of perspiration might soon be enough to identify a criminal or diagnose a cancer. But this fast-moving science could also pose a serious threat to civil liberties

When I deposited my index fingerprint on a laboratory slide so that Simona Francese could analyse it, I felt as if I was giving her the password to my body’s secrets. Most forensic scientists examine a fingerprint’s pattern but Francese, a forensic scientist from Sheffield Hallam University, analyses the chemicals left behind in those whirls and swirls. Her aim is to develop techniques that will allow her to extract identifying information about people at a crime scene from the sweaty residues they leave behind.

Fingerprints are inked with sweat, a body fluid that holds revealing information about our health and our vices. Our sweat glands source perspiration from the watery parts of blood, and any chemicals flowing around your circulatory system can, in principle, leak out of your sweat pores.