Combined evidential value of forensic DNA profiles

Combined evidential value of forensic DNA profiles

De Zoete, J.C.

Cator, E.A. (mentor)

Electrical Engineering, Mathematics and Computer Science

Statistics

2012-06-08

In forensic science it is common practice to work on problems where the likelihood ratio is based on observing single piece of evidence given two hypotheses. However, in a lot of cases, there is more than one piece of evidence. In this thesis three problems regarding combining DNA profiles are discussed. First, we derived a method to combine the evidential value of different partial Y-chromosomal DNA profiles of different stains. The method consists of finding a lower bound for the likelihood ratio when more than two propositions are compared and where we don't need the prior probabilities of the different propositions. Second, we made a simulation model to investigate the dendence of autosomal and Y chromosomal DNA profiles by assuming that everybody with the same Y-chromosomal DNA profile has a common ancestor and simulating the assignment of autosomal DNA profiles over different family tree structures. The results can be used in practice as scientific support for the assumption of independence between the Y and autosomal profile. Third, we developed a model to interpret (low-template) DNA profiles which is able to give the likelihood of observing the DNA profile given any allele-combination of the donor. This model assumes that a DNA profile is a result of a stochastic process where the input are the alleles of a possible donor. This model uses the information in peak heights without using any threshold. The model shows promising results in determining the combined evidential value of several low template DNA profiles that were obtained from the same stain.

Combining Evidence
forensic
DNA profiles

http://resolver.tudelft.nl/uuid:5164244e-62cc-43ba-b45e-cd47275ed167

Student theses

master thesis

(c) 2012 De Zoete, J.C.