Y-profile evidence

Close paternal relatives and mixtures

Mikkel Meyer Andersen, David J. Balding

Research output: Contribution to journalJournal articleResearchpeer-review

1 Citation (Scopus)

Abstract

We recently introduced a new approach to the evaluation of weight of evidence (WoE) for Y-chromosome profiles. Rather than attempting to calculate match probabilities, which is particularly problematic for modern Y-profiles with high mutation rates, we proposed using simulation to describe the distribution of the number of males in the population with a matching Y-profile, both the unconditional distribution and conditional on a database frequency of the profile. Here we further validate the new approach by showing that our results are robust to assumptions about the allelic ladder and the founder haplotypes, and we extend the approach in two important directions. Firstly, forensic databases are not the only source of background data relevant to the evaluation of Y-profile evidence: in many cases the Y-profiles of one or more relatives of the accused are also available. To date it has been unclear how to use this additional information, but in our simulation-based approach its effect is readily incorporated. We describe this approach and illustrate how the WoE that a man was the source of an observed Y-profile changes when the Y-profiles of some of his male-line relatives are also available. Secondly, we extend our new approach to mixtures of Y-profiles from two or more males. Surprisingly, our simulation-based approach reveals that observing a 2-male mixture that includes an alleged contributor's profile is almost as strong evidence as observing a matching single-contributor evidence sample, and even 3-male and 4-male mixtures are only slightly weaker.
Original languageEnglish
JournalForensic Science International: Genetics
Volume38
Pages (from-to)48-53
Number of pages6
ISSN1872-4973
DOIs
Publication statusPublished - 1 Jan 2019

Fingerprint

Databases
Weights and Measures
Y Chromosome
Information Storage and Retrieval
Mutation Rate
Haplotypes
Population
Direction compound

Keywords

  • forensic genetics
  • Y-chromosome
  • population genetics
  • weight of evidence
  • mixed profiles
  • relatedness
  • STR loci

Cite this

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title = "Y-profile evidence: Close paternal relatives and mixtures",
abstract = "We recently introduced a new approach to the evaluation of weight of evidence (WoE) for Y-chromosome profiles. Rather than attempting to calculate match probabilities, which is particularly problematic for modern Y-profiles with high mutation rates, we proposed using simulation to describe the distribution of the number of males in the population with a matching Y-profile, both the unconditional distribution and conditional on a database frequency of the profile. Here we further validate the new approach by showing that our results are robust to assumptions about the allelic ladder and the founder haplotypes, and we extend the approach in two important directions. Firstly, forensic databases are not the only source of background data relevant to the evaluation of Y-profile evidence: in many cases the Y-profiles of one or more relatives of the accused are also available. To date it has been unclear how to use this additional information, but in our simulation-based approach its effect is readily incorporated. We describe this approach and illustrate how the WoE that a man was the source of an observed Y-profile changes when the Y-profiles of some of his male-line relatives are also available. Secondly, we extend our new approach to mixtures of Y-profiles from two or more males. Surprisingly, our simulation-based approach reveals that observing a 2-male mixture that includes an alleged contributor's profile is almost as strong evidence as observing a matching single-contributor evidence sample, and even 3-male and 4-male mixtures are only slightly weaker.",
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Y-profile evidence : Close paternal relatives and mixtures. / Andersen, Mikkel Meyer; Balding, David J.

In: Forensic Science International: Genetics, Vol. 38, 01.01.2019, p. 48-53.

Research output: Contribution to journalJournal articleResearchpeer-review

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