separating familial mixtures, one genotype at a time northeastern association of forensic scientists...
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Separating Familial Mixtures, One Genotype at a Time
Northeastern Association of Forensic ScientistsNortheastern Association of Forensic ScientistsNovember, 2014November, 2014
Hershey, PAHershey, PA
Ria David, PhD, Martin Bowkley, MS, Ria David, PhD, Martin Bowkley, MS, and Mark W Perlin, PhD, MD, PhDand Mark W Perlin, PhD, MD, PhD
Cybergenetics, Pittsburgh, PACybergenetics, Pittsburgh, PA
Cybergenetics © 2003-2014Cybergenetics © 2003-2014
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Relatives share alleles
a b c d
First person’s allele pair
Second Second person's person's allele pairallele pair
Third person’s allele pair
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Cybergenetics experience
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People of New York v Father of two daughters
Five semen stains on a comforter
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STR dataQuantitative peak heights at locus D16S539
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TrueAllele® Casework
ViewStationUser Client
DatabaseServer
Interpret/MatchExpansion
Visual User InterfaceVUIer™ Software
Parallel Processing Computers
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Mixture separation
Father
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Genotype separationConsider every possible genotype solution
One person’s allele pair
Another person’s Another person’s allele pairallele pair
Explain thepeak pattern
Better explanationhas a higher likelihood
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Minor genotypeObjective genotype determined solely from the DNA data.
Never sees a comparison reference.
99%
0.1%0.1%
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Match statistic at locusHow much more does the victim match the evidence
than a random person?
Prob(evidence match)
Prob(coincidental match)
15x99%
7%
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Reported match statistics
A match between the comforterand the young girl is
186 quadrillion times more probable than coincidence
Multiply together the LR’s at every locus
A match between the comforterand the girl's father is
33 quadrillion times more probable than coincidence
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Separate father as contributorlo
g(LR
)
item (contributors)
90% 90% 50% 50% 70%
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Separate daughter as contributorlo
g(LR
)
item (contributors)
10% 10% 50% 50% 30%
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Assume father, separate daughterlo
g(LR
)
item (contributors)
10% 10% 50% 50% 30%
peeling procedure
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Published validation papersPerlin MW, Sinelnikov A. An information gap in DNA evidence interpretation. PLoS ONE. 2009;4(12):e8327.
Ballantyne J, Hanson EK, Perlin MW. DNA mixture genotyping by probabilistic computer interpretation of binomially-sampled laser captured cell populations: Combining quantitative data for greater identification information. Science & Justice. 2013;53(2):103-14.
Perlin MW, Hornyak J, Sugimoto G, Miller K. TrueAllele® genotype identification on DNA mixtures containing up to five unknown contributors. Journal of Forensic Sciences. 2015;in press.
Greenspoon SA, Schiermeier-Wood L, Jenkins BC. Establishing the limits of TrueAllele® Casework: a validation study. Journal of Forensic Sciences. 2015;in press.
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):1430-47.
Perlin MW, Belrose JL, Duceman BW. New York State TrueAllele® Casework validation study. Journal of Forensic Sciences. 2013;58(6):1458-66.
Perlin MW, Dormer K, Hornyak J, Schiermeier-Wood L, Greenspoon S. TrueAllele® Casework on Virginia DNA mixture evidence: computer and manual interpretation in 72 reported criminal cases. PLOS ONE. 2014;(9)3:e92837.
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TrueAllele in the United StatesLaboratory systems or case reports in 23 states
initialfinal
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Court acceptance
• California• Ohio• Pennsylvania• Virginia
• United Kingdom• Australia
Appellate precedent in Pennsylvania
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35% 28%
8% 4%25%
Separate out 5 relatives from a homicide mixture
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35% 28%
8% 4%25%
Infer 5 unknown genotypes:match 35% contributor
13
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35% 28%
8% 4%25%
Assume 1 known, infer 4 unknown: match 28% contributor
13 7
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35% 28%
8% 4%25%
Assume 2 known, infer 3 unknown:match 25% contributor
13 7
9
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35% 28%
8% 4%25%
Assume 3 known, infer 2 unknown:match 8% contributor
13 7
9 2
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35% 28%
8% 4%25%
Assume 4 known, infer 1 unknown:match 4% contributor
13 7
9 2 4
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