Applications of SNPs to forensics

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Applications of SNPs to forensics

• Thore Egeland
• Rikshospitalet Section of Medical Statistics,
  UiO
• Collaborators
• Bente Mevåg, Inst of Forensic medicine, UiO
• Angel Carracedo, Santiago de C, Spain
• Geir Dahl, Geir Storvik, UiO,
• Petter Mostad, Göteborg
• ...

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Contents

• Forensic genetics
• Criminal cases
• Mixture evidence, current practice
• SNPs, potential benefits
• Future projects?

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Forensic genetics. Family cases
Freewarehttp//www.nr.no/familias Used in
forensic laboratories in more than 10 countries
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Forensic genetics. Biological evidence Criminal
cases involving DNA, Norway
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Problems with traditional methods

• "The interpretation of these mixtures can be a
  challenging task for the DNA scientist". Ladd et
  al (2001)
• "Powerful methods based on likelihood ratios have
  been developed by Evett et al.(1) and Weir et
  al.(2) to interpret mixtures. However, these
  models presuppose unambiguous identification of
  alleles prior to analysis and take no account of
  their relative peak areas." Gill et al

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Why SNP-s?

• Problems of interpretation reduced?
• May work better than STRs for degraded biological
  material.
• Eventually, cheaper and better suited on a large
  scale
• Many available, may compensate for less
  variability.

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Three main statistical problems

• How many markers are needed to1. exclude
  innocent, 2. determine genotypes of
  contributors to a stain, 3. obtain sufficiently
  strong evidence

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Example. Future application

• A rape has been commited. The genotype of the
  rapist is determined and used as input to search
  a database of previous convicts.

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Suggestions for project proposal

• Design and analyze (in laboratory) controlled
  experiments.
• Determine, develop and implement if necessary,
  suitable methods.
• Analyze data.Competence in many fields
  required Biology, Informatics, Forensics,
  Statistics, ...

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References

• Evett and Weir (1998). Interpreting DNA
  evidence. Sinauer, MA, USA.
• Weir (1995). DNA statistics in the Simpson
  matter. nat gen, 11, 366-368
• www.nr.no/familias and references therein
• Egeland, Dalen and Mostad. To appear in Int J
  Legal Medicine, 2003.