Dr. Amke Caliebe
Forensic DNA Phenotyping
Was |
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Wann |
14.07.2017 von 12:00 bis 13:00 |
Wo | Eckerstraße 1, Raum 404, 4. OG |
Termin übernehmen |
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Forensic DNA Phenotyping (FDP) is a relatively new
development in the field of forensic genetics. It aims at predicting
selected so-called externally visible characteristics (EVCs) of a
trace donor from their DNA as left behind at the crime scene. The
best results for FDP were achieved for eye
colour where the
IrisPlex DNA test system was developed
(Walsh
et al. 2011), which includes six SNPs
in six different genes, and was found to obtain relatively high
levels of prediction. The second best predictable EVC after eye
colour is hair
colour.
In the first part of this talk,
results of a study investigating the prediction of the pigmentation
phenotypes eye, hair and skin colour in a Northern German population
will be presented (Caliebe
et al. 2016). With this study, we
aimed at answering the following research questions: (1) do existing
models allow good prediction of high-quality phenotypes in a
genetically similar albeit more homogeneous population? (2) Would a
model specifically set up for the more homogeneous population perform
notably better than existing models? (3) Can the number of markers
included in existing models be reduced without compromising their
predictive capability in the more homogenous population?
In
the second part of the talk we differentiate FDP from trace donor
identification problems. In the latter, it has become widely accepted
in forensics that, owing to a lack of sensible priors, the evidential
value of matching DNA profiles is most sensibly communicated in the
form of a likelihood ratio (LR). This agreement is not in
contradiction to the fact that the posterior odds (PO) would be the
preferred basis for returning a verdict. A completely different
situation holds for FDP. The statistical models underlying FDP
typically yield PO for an individual possessing a certain EVC. This
apparent discrepancy has led to confusion as to when LR or PO is the
appropriate outcome of forensic DNA analysis to be communicated. We
thus set out to clarify the distinction between LR and PO in the
context of forensic DNA profiling and FDP from a statistical point of
view (Caliebe
et al. 2017).
Caliebe, A., M. Harder, R. Schuett, M. Krawczak, A. Nebel and N. von Wurmb-Schwark, 2016. The more the merrier? How a few SNPs predict pigmentation phenotypes in the Northern German population. Eur. J. Hum. Genet. 24: 739-747.
Caliebe, A., S. Walsh, F. Liu, M. Kayser and M. Krawczak, 2017. Likelihood ratio and posterior odds in forensic genetics: Two sides of the same coin. Forensic Sci Int Genet 28: 203-210.
Walsh, S., F. Liu, K. N. Ballantyne, M. van Oven, O. Lao and M. Kayser, 2011. IrisPlex: a sensitive DNA tool for accurate prediction of blue and brown eye colour in the absence of ancestry information. Forensic Sci Int Genet 5: 170-180.