the Metropolitan Police and head of the Criminal Investigation Department took over the case. Aside from the lack of forced entry as well as the empty cash box, it was clear that Mr and Mrs Farrow had been attacked separately and the discovery of two black masks fashioned from stockings that were left at the scene indicated that there were two men involved. Since the victims were in their night clothes, the police had speculated that Mr Farrow was deceived into opening the door while he was still half asleep. He was immediately attacked, but was still conscious enough to go after the robbers, and was hit again. His assailants went up to the upstairs flat, attacked Mrs Farrow, located the cash box, and fled with the money. However, based on the separate pools of blood at the scene, it was determined that Mr Farrow had again regained consciousness, and this time the men killed him and afterwards washed their hands in a nearby basin. A greasy smudge on the cash box When MacNaghten was told of the empty cash box, he chose to examine it. He noticed that on the underside of the box's inner tray, there was a greasy smudge which appeared to be a fingerprint. As a member of the Belper Committee which had recommended the use of fingerprints as a method for identification five years before, he wondered if this might be a case to test out this new technique. He used his handkerchief to carefully pick up the cash box, had it wrapped in paper and took it into the fledgling Fingerprinting Bureau at Scotland Yard. Established on 1 July 1901, the Fingerprint Bureau had proven its worth with the conviction a year later of Harry Jackson for burglary, thanks to fingerprint evidence. It was now headed by Detective Inspector Charles Stockley Collins who was regarded as the foremost English fingerprint expert of his time. Despite its earlier successes, especially in identifying previously convicted criminals who tried to pass themselves off pseudonymously, the technique was still considered unwieldy and both men knew that they were risking public ridicule with the intense scrutiny that a murder case would generate. Furthermore, even if they succeeded in identifying the owner of the fingerprint, they still needed to convince a potential jury sufficiently to convict. Detective Inspector Collins examined the print thoroughly and determined that the print was made