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A new ten-locus STR (short tandem repeat) profiling system was recently introduced into casework by the Forensic Science Service (FSS) and statistical analyses are described here based on data collected using this new system for the three major racial groups of the UK: Caucasian. Afro-Caribbean and Asian (of Indo-Pakistani descent). Allele distributions are compared and the FSS position with regard to routine significance testing of DNA frequency databases is discussed. An investigation of match probability calculations is carried out and the consequent analyses are shown to provide support for proposed changes in how the FSS reports DNA results when very small match probabilities are involved.

A previous paper in this journal has described the conventional statistical analysis of three databases (Caucasian, Afro-Caribbean and Asians from the Indian subcontinent) where individuals are typed at six short tandem repeat (STR) loci. This paper presents a Bayesian analysis of the same data and the approach is centred on the concept of estimating coancestry coefficients from mixed databases. Posterior distributions for the three databases are presented and the discussed and the consequences of implementing bootstrap estimation procedures are also shown.

Data have been collected from 602 Caucasians, 190 Afro-Caribbeans and 257 Asians of Indo/Pakistani descent who have been profiled using a new six locus short tandem repeat (STR) multiplex. The data have been analysed by conventional significance testing methods: the exact test, homozygosity, and conventional goodness of fit to Hardy-Weinberg proportions. Frequency tables are given and the expected performance in British forensic casework is discussed.

Data from nearly 2500 British Caucasians, profiled using an STR quadruplex, have been analysed. The data came from several laboratories and represent samples from different geographical distributions. Analysis of the combined files shows that previous reports of failed independence tests were the results of sampling effects. A further convincing proof is given of the robustness of the statistical methods used to estimate evidential value in casework. Comparisons between different samples show that regional effects between Scotland and the South of England have no importance from the forensic viewpoint.

Over 5,700 three-probe VNTR DNA profiles collected by several United Kingdom (UK) laboratories have been compared to examine the probability of randomly matching 2 samples from different individuals. In over 16 million comparisons, using a matching rule corresponding to the matching guideline employed by the UK Forensic Science Service, no profiles were found to match at the 3 loci D1S7 (MS1), D7S21(MS31) and D12S11 (MS43a). The frequency of occurrence of a set of Caucasian profiles have been estimated with 6 reference databases. The results show that there were greater differences in the frequency estimates when using a database of Afro-Caribbean or Asian profiles, rather than a different Caucasian database. The results further demonstrate the power and robustness of the VNTR DNA profiling technique for forensic casework.

We describe a series of experiments, carried out on data from DNA profiles, which have been designed specifically to test the validity of the statistical procedures currently used in the Home Office Forensic Science Service. The tests address issues which have been the subject of topical debate, in particular those of representativeness and band independence. The results confirm the confidence which had already been placed in the established procedures. We recommend that all practitioners in the forensic field should carry out similar testing on their own data collections.