By the end of the nineteenth century everyday machines ranging from bicycles and typewriters to watches and sewing machines were increasingly becoming part of Indian lives. As the heartland of British power in the region, the Bengal Presidency was particularly well-served by the percolation of everyday machines. Naturally, some of these machines soon became part of the hardware of criminal operations. Anonymous ransom notes were written on typewriters, robbers fled on bicycles and sewing needles were used as murder weapons. This is what I call technocriminality, viz. criminality that was crucially constituted by the deployment of technological objects and knowledge. By necessity, those tasked with fighting such technocriminality had to evolve new modes of detection. Ways had to be found for distinguishing one typewriter from another, to recognize one bicycle track from another etc. As a result there evolved what I dub machinic forensics. Technocriminality and machinic forensics were mutually co-constituted through their opposition. Every time the one advanced the other had to catch up. If the detectives were ahead, the criminals found new ways to cover their tracks and if the criminals were on top the detectives had to upgrade their methods. By looking at criminality and forensics as mutually constitutive and by fore-staging technological objects in their relationship, I believe we can unravel a hitherto neglected dimension of forensics: away from its usual focus on the internal dynamics of the development of individual techniques. By drawing upon police records, memoirs of police officers, news-reports and crime fiction, I shall demonstrate how everyday technological objects became the crucial link connecting technocriminality and machinic forensics in a process of escalating mutual evolution.