Single Source Samples
This chapter considers the interpretation of single source samples. A distinction is drawn in the minds of forensic practitioners between single source and mixed samples. Single sourced deoxyribonucleic acid (DNA) samples may have any number of template molecules. The chapter deals with the forensic analysis of low levels of DNA. It discusses changes in profile morphology that occur when there are very few starting templates and the issue of contamination. A consensus profile is one where an allele is only reported provided that it appears in at least two replicate analyses — where replicates are typically carried out in duplicate or in triplicate. The decision as to how many individuals are present in the consensus profile is one of the more problematic decisions in low copy number casework. The argument extends straightforwardly to the concept of dropping loci in either single source or mixed profiles.