This chapter details the current legal provisions and professional guidelines governing the use of genetic testing and DNA samples in the administration of criminal justice in the United Kingdom (UK). It covers the provisions that operate in the main jurisdictions of the UK: England and Wales, Northern Ireland and Scotland. For each jurisdiction, the chapter is divided into sections that together address all of the questions posed in the questionnaire on the uses of DNA testing in criminal trials. The high degree of objective certainty that DNA evidence can provide has meant that it has come to play an increasingly prominent role in the investigation of crime and the conduct of criminal prosecutions in the UK. Since 1992, there has existed the National Crime Intelligence Service, which has brought police forces from around the country together with Customs & Excise to collect, develop and analyse information in order to provide criminal intelligence that is more pro-active, organised and efficient.