Statistical Analysis of Complex Forensic DNA Cases

Seminar in applied mathematics and statistics.

Statistical analysis of complex forensic DNA cases

SPEAKER:

Julia Mortera, Universita Roma Tre

ABSTRACT: 

DNA is now routinely used in criminal and civil investigations. DNA
samples are of varying quality and therefore present challenging problems
for their interpretation. We present a statistical model for the quantitative
peak information obtained from an electropherogram (EPG) of a forensic
DNA sample and illustrate its potential use for the analysis of civil and
criminal cases. In contrast to most previously used methods, we directly
model the peak height information and incorporate important artefacts as-
sociated with the production of the EPG. Our model has a number of un-
known parameters, and we show that these can be estimated by the method
of maximum likelihood in the presence of multiple unknown contributors,
and their approximate standard errors calculated; the computations exploit
a Bayesian network representation of the model.

A case example of disputed paternity, where a mixed DNA sample is
taken from an exhumed bone, is used to illustrate the ecacy of the model.
The deconvolution of the mixture is necessary for nding the most likely
DNA prole of the putative father and also to compute the likelihood ratio of
paternity versus non-paternity. We also show some results when introducing
uncertainty in allele frequencies.

Based on joint work with Therese Graversen, Peter Green, Steen Lau-
ritzen and Robert Cowell.

Tea and chocolate will be served in room 04.3.15 after the seminar.