DNA and the Active Criminal Population

Analysis of rates of submission of crime scene samples from one police force area and of matches with offender DNA samples already on the national database demonstrates, first, an increasing rate of submission, second, a steady state of matching in the West Midlands force during the period studied, at 58 per cent, and third, a reasonable linear fit between number of samples and number of matches, suggesting no diminution in return as the number of submitted samples increased. The results are discussed in terms of the distribution of lengths of criminal career; implications for practice are also discussed, especially the importance of taking criminal justice samples at the first presenting opportunity.