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Finding Truth in DNA Mixture Evidence Innocence Network Conference April, 2013 Charlotte, NC Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA.

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Presentation on theme: "Finding Truth in DNA Mixture Evidence Innocence Network Conference April, 2013 Charlotte, NC Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA."— Presentation transcript:

1 Finding Truth in DNA Mixture Evidence Innocence Network Conference April, 2013 Charlotte, NC Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA Cybergenetics ©

2 DNA Mixture Data Quantitative peak heights at a locus peak size peak height

3 Peak Thresholds Threshold Under threshold, don't use alleles Allele Pair 7, 7 7, 10 7, 12 7, 14 10, 10 0%10, 12 10, 14 12, 12 12, 14 14, 14 Simplify data for human review

4 Allele Dropout Threshold Under threshold, use alleles anyway Allele Pair 7, 7 7, 10 7, 12 7, 14 10, 10 > 0% 10, 12 10, 14 12, 12 12, 14 14, 14 Conjure phantom peaks

5 Human Interpretation Issues Evidence call good data inconclusive peaks are too low for them too many contributors to handle potential examination bias Database hit by association, not by match comparison: make false hits restrict upload: lose true hits

6 TrueAllele ® Casework Evidence preserve data information use all peaks, high or low any number of contributors entirely objective, no bias Database hit based on LR match statistic sensitive: find true hits specific: only true hits

7 Validation Studies Perlin MW, Sinelnikov A. An information gap in DNA evidence interpretation. PLoS ONE. 2009;4(12):e8327. Perlin MW, Legler MM, Spencer CE, Smith JL, Allan WP, Belrose JL, Duceman BW. Validating TrueAllele ® DNA mixture interpretation. Journal of Forensic Sciences. 2011;56(6): Perlin MW, Belrose JL, Duceman BW. New York State TrueAllele ® Casework validation study. Journal of Forensic Sciences. 2013;58(6):in press.

8 Separate Mixture Contributors 25%75%

9 Genotype Thorough: consider every possible genotype solution Objective: does not know the comparison genotype Explain the peak pattern Better explanation has a higher likelihood Victim's allele pair Another person's allele pair Allele Pair 7, 7 7, 10 7, 12 7, 14 10, 10 98%10, 12 10, 14 12, 12 12, 14 14, 14

10 locus TH01 Three person mixture Lab says: inconclusive

11 TrueAllele mixture interpretation Genotype probability distribution Thorough & objective

12 Handgun does NOT match suspect Computer statistic AGAINST match

13 Informative TrueAllele genotype Expected match statistic: million/billion Search a DNA database for the right man?

14 The Search for Truth M. W. Perlin, "When good DNA goes bad," Journal of Forensic Research, S11:003, M. W. Perlin, "DNA Identification Science," in Forensic Sciences, volume 3. C. H. Wecht, Ed., Albany, NY: LexisNexis Matthew Bender, Chapter 37C, M. W. Perlin. "Forensic science in the information age." Forensic Magazine, 9(2):17-21, 2012.

15 More information Courses Newsletters Newsroom Presentations Publications


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