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![Page 1: DNA Mixture Interpretations and Statistics – To Include or Exclude Cybergenetics © 2003-2013 Prescription for Criminal Justice Forensics ABA Criminal Justice.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513f13d55034646298b605c/html5/thumbnails/1.jpg)
DNA Mixture Interpretations and Statistics –
To Include or Exclude
Cybergenetics © 2003-2013Cybergenetics © 2003-2013
Prescription for Criminal Justice ForensicsABA Criminal Justice Section
New York, NYNew York, NYJune, 2013June, 2013
Mark W Perlin, PhD, MD, PhDMark W Perlin, PhD, MD, PhDCybergenetics, Pittsburgh, PACybergenetics, Pittsburgh, PA
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CHILD&
CHILD
CHILD&
CHILDCHILD
VICTIM
Television
Cabinet
Table
Table
L-Shaped Couch
Bathroom
Bed
room
Lau
ndry
Bed
room
StairsBookcase
VICTIM
VICTIM
Storage
Door to OutsideCloset
underpants
pajama pants
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DNA mixture dataQuantitative peak heights at a locus
peak size
peakheight
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Peak thresholds
Threshold
Under threshold, don't use alleles
Allele Pair7, 77, 107, 127, 14
10, 100%10, 12
10, 1412, 1212, 1414, 14
Simplify data for manual review
![Page 5: DNA Mixture Interpretations and Statistics – To Include or Exclude Cybergenetics © 2003-2013 Prescription for Criminal Justice Forensics ABA Criminal Justice.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513f13d55034646298b605c/html5/thumbnails/5.jpg)
Allele dropout
Threshold
Under threshold, use alleles anyway
Allele Pair7, 77, 107, 127, 14
10, 10> 0% 10, 12
10, 1412, 1212, 1414, 14
Conjure phantom peaks
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Manual interpretation issues
Evidence• call good data inconclusive• peaks are too low for methods• too many contributors to handle• potential examination bias
Database• hit by association, not by match• comparison: make false hits• restrict upload: lose true hits
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TrueAllele® genotype model
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
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Mixture weightSeparate mixture data into its contributor components
25% 75%
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Genotype inferenceThorough: consider every possible genotype solutionObjective: does not know the comparison genotype
Explain thepeak pattern
Betterexplanationhas ahigher likelihood
Victim's allele pair
Another person's Another person's allele pairallele pair
![Page 10: DNA Mixture Interpretations and Statistics – To Include or Exclude Cybergenetics © 2003-2013 Prescription for Criminal Justice Forensics ABA Criminal Justice.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513f13d55034646298b605c/html5/thumbnails/10.jpg)
Match information
Probability(evidence match)
Probability(coincidental match)
How much more does the suspect match the evidencethan a random person?
30x
3%
98%
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TrueAllele inclusionFinds the right answer
11
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Thresholds lose informationUnderstate the probative force
2 6
ThresholdStochastic Threshold
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TrueAllele exclusionDoes not find the wrong answer
– 20
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TrueAllele usage
• child molester got: 20 quadrillion match, 22 years• validation study: 4 peer-reviewed scientific papers• admissibility: Pennsylvania, California, N. Ireland• precedent: Pennsylvania appellate ruling• approval: NYS Commission on Forensic Science• cases: over 100 reports in criminal cases• trials: over 15 (rape, murder, terror, weapons, ...)
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TrueAllele deployment
Casework systemInterpretation services
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DNA truth, criminal justiceThis truth is incontrovertible. Panic may resent it, ignorance may deride it, malice may distort it, but there it is. - Winston Churchill
Police effective databaseProsecutor convict the guiltyDefender exonerate innocentCourt the whole truthCitizen prevent crime
Genotype models are more accurate. Who cares?
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