My grandfather, Herbert Alden (right) Fingerprint Dept, Scotland Yard

Further reading
Much of the blood and explanation revolves around the horrific murder of Thomas and Ann Farrow in 1905, which the newspapers dubbed The Shocking Tragedy of Deptford. Burglars had broken into Chapman’s Oil and Colour Shop and killed the manager Mr Farrow, who was left with his head smashed, blood running into the hearth and soaking the ashes.

Mrs Farrow, who was also brutally beaten, clung to life, and the police thought they had a witness, but she died without regaining consciousness. The case seemed insoluble, until Scotland Yard Assistant Commissioner Melvile Macnaghten stumbled upon the shop’s cashbox hidden under Mr Farrow’s bed. It was adorned with a single fingerprint. The challenge was not only to identify the owner of the print, but to convince a British jury for the first time that they should send a man to the gallows on the evidence of, as Beavan puts it, “a gob of sweat smeared on a piece of metal”.

Fascinating piece of history and forensics. Excellent.

Thanks, Tr!