Taking account of peak areas when interpreting mixed DNA profiles

This paper establishes a logical framework for taking account of peak areas when interpreting mixed DNA STR profiles. The principles apply wherever such data are available but they are illustrated here by means of data which have been collected from made up mixtures of known concentrations analyzed at short tandem repeat loci. The data have led to some modeling assumptions which are used for numerical examples. In actual casework the proportions of the various components will not be known and there is a discussion of whether they should be allowed for by integrating over a prior distribution. This is a conceptual paper, rather than a prescription for casework, and the scope for further work is outlined.