chapter  8
48 Pages

Complex Profiles

ByJohn S. Buckleton, Duncan Taylor, Peter Gill, James M. Curran, Jo-Anne Bright

This chapter deals with the analysis of complex deoxyribonucleic acid (DNA) profiles. The analysis of forensic stains will inevitably lead to mixtures of DNA from different individuals, as a result of the mixing of body fluids and secretions. The recognition, resolution and statistical evaluation of such mixtures are therefore integral and vital parts of forensic casework. Low template levels are known to lead to substantial changes to profile morphology such as greater peak imbalance, dropout and, at enhanced sensitivity, the almost unavoidable appearance of contaminant alleles. The addition of the subpopulation correction to mixtures is based on the application of the sampling formula. The subpopulation model works best when those people who share the same subpopulation as the suspect are used in the conditioning. The chapter presents a matter relating to the prevalent use of the words excluded, not excluded and included.