Statistical Methods Employed in Evaluation of Single-Locus Probe Results in Criminal Identity Cases

Evaluation of single-locus probe results in criminal-identity cases is best presented within the standard forensic framework for handling trace evidence. A comprehensive account was given by Aitken (1 ), and the language of that text will be used here. For simplicity, suppose a stain from the scene of the crime has DNA profile type A that is known to be from the perpetrator P of the crime. Person S , who is a suspect in the crime, has profile B. In the conventional treatment, S is removed from suspicion if B ≠ A , although this matchbased approach can be avoided with a continuous treatment (2 ). If there is a match between the stain and suspect profiles, A = B , the evidence of the match is denoted by E. There are two explanations for E :

1.	C: Person S is the perpetrator P (usually the prosecution explanation).
2.	C : Person S is not the perpetrator P (usually the defense explanation).