Evidential value of a Y-STR profile match: The Neighbor-Matching Method

Y-haplotype profiling presents special advantages for forensic casework, paternity and population studies. Y-chromosome DNA is male-specific and can sometimes be detected in stains where autosomal DNA cannot. When a suspect in a criminal case has the same Y-haplotype as found in a crime stain, what is the evidential value of the match? In such cases, knowing an estimate of the frequency of the suspect's haplotype in the population is of interest. Many solutions to find such an estimate have been proposed but never accepted by the entire forensic experts population. In this report we present a new method, called the Neighbor-Matching method, as well as a detailed comparison with the existing methods and a theoretical analysis of these methods. The Neighbor-Matching method uses a population evolution process to estimate which haplotypes genetically close to the suspect's haplotype, called neighbors, are expected to be in the population if the suspect's haplotype is common or rare. No assumptions are made as to the distribution of all haplotype frequencies in the population, and as much genetical information as possible is used to create the neighbors. After the analyze of the theoretical and numerical results, it appears that this new method is well adapted to the problem at hand and quite robust to changes in its parameters, so can be seen as reliable. However, the version presented in this report is a simplified prototype, and more work has to be done to create a program largely usable by forensic experts.

Subject

Y-STR haplotype
forensic science
forensic statistics
DNA
match probability estimation
haplorype frequency

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http://resolver.tudelft.nl/uuid:acec4393-801e-4432-8e60-88081673cc70

Embargo date

2011-06-30

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Student theses

Document type

master thesis

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