more informative dna identification: computer reinterpretation of existing data ria david, phd...
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More informative DNA identification:More informative DNA identification:Computer reinterpretation of Computer reinterpretation of
existing dataexisting data
Ria David, PhDRia David, PhDCybergenetics, Pittsburgh, PACybergenetics, Pittsburgh, PA
Cybergenetics © 2003-2010Cybergenetics © 2003-2010
Midwestern Association of Forensic Midwestern Association of Forensic Scientists 39th Annual MeetingScientists 39th Annual Meeting
October, 2010October, 2010
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SWGDAM 2010 SWDGAM guidelines, section 3.2.2
If a stochastic threshold based on peak height is not used in the evaluation of DNA typing results, the laboratory must establish alternative criteria (e.g.,
quantitation values or use of a probabilistic genotype approach) for addressing potential stochastic
amplification. The criteria must be supported by empirical data and internal validation and must be
documented in the standard operating procedures.
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TrueAllele® CaseworkComputer interpretation of DNA evidenceComputer interpretation of DNA evidenceby mathematically modeling STR processby mathematically modeling STR process
• objectivityobjectivity• • ease of useease of use• • informationinformation• • productivityproductivity
Primary goalsPrimary goals
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Interpretation MattersNational Institute of Standards and TechnologyTwo Contributor Mixture Data, Known Victim
31 thousand (4)
213 trillion (14)
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Preserving DNA Information Quantitative vs. Qualitative
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Data Classification
Mixture items assigned a degree of difficulty
Simple: two person mixture with a known victim
Medium: two unknown mixture samples
Complex: three or more unknown contributors, or a partial profile
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0
5
10
15
20
25
2A 2C 2H 2D 2B 2F 2G 2E
LR2
CPI
Information - two unknown
7.037.03
6.246.2413.2613.26
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Information - all mixtures
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Locus D21S11
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Quantitative TrueAllele
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Quantitative TrueAllele
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Quantitative TrueAllele
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Quantitative TrueAllele
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Qualitative Threshold
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Qualitative Threshold
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Qualitative Threshold
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Qualitative Threshold
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Stochastic Threshold
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Stochastic Threshold
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Stochastic Threshold
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13 Locus Statistic
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Conclusion
• Forensic analysts’ goal is to get identification information from their data to help solve cases
• SWGDAM guidelines make it more difficult for analysts to extract information from DNA data
• TrueAllele’s approach of probabilistic interpretation is allowed by the SWGDAM guidelines and extracts more identification information than human interpretation
• Using a probabilistic genotype interpretation would enable forensic analysts to better ensure public safety
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Acknowledgements
New York State PoliceBarry DucemanMelissa LeeShannon MorrisElizabeth Staude
CybergeneticsWilliam AllanMeredith ClarkeMatthew LeglerJessica SmithCara Spencer
Northeast RegionalForensics InstituteJamie Belrose