This chapter examines the use of Deoxyribonucleic acid (DNA) within criminal justice systems, with special reference to the United Kingdom (UK), where DNA profiling originated and became quickly embedded within the criminal process. The creation of DNA databases and the attendant issues raised will be considered. The use of DNA during an investigation provides an opportunity to place less reliance upon often questionable evidence, such as eye-witness testimony or confessions. The advent of forensic DNA testing has thus indeed been revolutionary, leading to the accurate detection and conviction of many criminals, who may otherwise have evaded punishment. In 2009, Italy passed DNA database legislation, permitting convicted offenders to have their DNA stored, and the DNA of arrested individuals could be taken upon the order of a judge, and later destroyed if not convicted. India's Union government was working on legislation in 2015 to set up a national DNA database of 'offenders'.