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TrueAllele Case Studies

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Presentation on theme: "TrueAllele Case Studies"— Presentation transcript:

1 TrueAllele Case Studies
TrueAllele® Workshop April, 2013 Leicestershire, United Kingdom Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA Cybergenetics © Cybergenetics ©

2 Murder in McKeesport October 25, 2008 Tamir Thomas

3 Biological evidence Cybergenetics © 3

4 DNA analysis PowerPlex® 16 STR Partial DNA profiles obtained for both
the gun and the cap

5 Human review results Match to Leland Davis Black 420 Caucasian 500
Hispanic 470 Black 5.7 quadrillion Caucasian 9.3 quadrillion Hispanic 1.8 quadrillion

6 Prosecutor question What is the true match information of the evidence
to the suspect?

7 TrueAllele® Casework ViewStation User Client Database Server
Interpret/Match Expansion Visual User Interface VUIer™ Software Parallel Processing Computers

8 TrueAllele operator STR evidence data .fsa genetic analyzer files
• Replicate computer runs for each item • Three unknown mixture contributors • Degraded DNA was considered Evidence genotypes probability distributions

9 TrueAllele report Genotype probability distributions Evidence genotype
Perlin MW. Explaining the likelihood ratio in DNA mixture interpretation. Promega's Twenty First International Symposium on Human Identification, 2010; San Antonio, TX. TrueAllele report Genotype probability distributions Evidence genotype Suspect genotype Likelihood ratio (LR) DNA match statistic Population genotype

10 TrueAllele DNA match LR match to Leland Davis Black 18.6 billion
Caucasian 12.1 billion Hispanic 3.37 billion Black 89 quadrillion Caucasian 420 quadrillion Hispanic 73.5 quadrillion

11 Trial preparation • case report • direct examination
• PowerPoint slides • background reading • other questions

12 TrueAllele reports 2 & 3 2. Is Dominick Haynes in the DNA evidence?
Answer: No – million factor against. 3. Is anyone else in both DNA evidence items? Answer: No – Leland Davis is the only one.

13 No pretrial admissibility hearing
TrueAllele precedent Commonwealth of Pennsylvania v. Kevin James Foley Superior Court, 2012

14 Computer Interpretation of Quantitative DNA Evidence
Commonwealth v Leland Davis August, 2012 Pittsburgh, Pennsylvania Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA Cybergenetics © Cybergenetics ©

15 DNA genotype 8, 9 A genetic locus has two DNA sentences,
one from each parent. An allele is the number of repeated words. locus A genotype at a locus is a pair of alleles. mother allele 1 2 3 4 5 6 7 8 8, 9 ACGT repeated word Many alleles allow for many many allele pairs. A person's genotype is relatively unique. father allele 1 2 3 4 5 6 7 8 9

16 DNA evidence interpretation
Lab Infer Evidence item Evidence data Evidence genotype 10, 50% 11, 30% 12, 20% Compare Known genotype 10, 12

17 Computers can use all the data
Quantitative peak heights at locus vWA peak size peak height

18 People may use less of the data
Over threshold, peaks are labeled as allele events All-or-none allele peaks, each given equal status Threshold Under threshold, alleles vanish

19 How the computer thinks
Consider every possible genotype solution One person's allele pair Explain the peak pattern Another person's allele pair A third person’s allele pair Better explanation has a higher likelihood

20 Objective genotype determined solely from the DNA data.
Evidence genotype Objective genotype determined solely from the DNA data. Never sees a suspect. 91% 1% 3% 1% 1% 2%

21 How much more does the suspect match the evidence
DNA match information How much more does the suspect match the evidence than a random person? 8x 91% Probability(evidence match) Probability(coincidental match) 11%

22 Match information at 15 loci

23 Is the suspect in the evidence?
A match between the handgun and Leland Davis is: 18.6 billion times more probable than a coincidental match to an unrelated Black person 12.1 billion times more probable than a coincidental match to an unrelated Caucasian person 3.37 billion times more probable than a coincidental match to an unrelated Hispanic person

24 Is the suspect in the evidence?
A match between the baseball cap and Leland Davis is: 89 quadrillion times more probable than a coincidental match to an unrelated Black person 420 quadrillion times more probable than a coincidental match to an unrelated Caucasian person 73.5 quadrillion times more probable than a coincidental match to an unrelated Hispanic person

25 Is anyone else in both items of evidence?
There is no indication that any person, other than Leland Davis, contributed their DNA to both items of evidence.

26 Verdict Leland Davis was convicted of third degree murder and weapons charges in the 2008 McKeesport slaying of Tamir Thomas.

27 Gang crime in Bakersfield
Perlin MW. DNA mapping the crime scene: do computers dream of electric peaks? Promega's Twenty Third International Symposium on Human Identification, 2012; Nashville, TN. Gang crime in Bakersfield Food mart • gun • hat

28 Escalation Food mart • gun • hat Jewelry • counter • safe Hardware
• phone

29 Jewelry store

30 Evidence from multiple scenes
Market • hat 1 • hat 2 • overalls • shirt Food mart • gun • hat Jewelry • counter • safe Convenience • keys • tape Hardware • safe • phone

31 DNA evidence: genotypes
First contributor 13 14 Second contributor DNA amount Third contributor 16 18 17 20 Allele size

32 Develop STR data First contributor Second contributor
Third contributor

33 Laboratory processing
12 evidence items Scene 1 Scene 2 Scene 3 Scene 4 Scene 5 • gun • hat • safe • phone • counter • keys • tape • hat 1 • hat 2 • overalls • shirt 10 reference items 5 victims • V1 • V2 • V3 • V4 • V5 5 suspects • S1 • S2 • S3 • S4 • S5

34 DNA match questions log(LR) Suspect 1 Suspect 2 Suspect 3 Suspect 4
1. Gun 1. Hat 2. Safe 2. Phone 3. Counter 3. Safe 4. Keys 4. Tape 5. Hat 1 5. Hat 2 5. Overalls 5. Shirt

35 Human review: no results
Above threshold, peak heights are ignored Below threshold, data unused

36 Computers dream of electric peaks
First contributor 13 14 Second contributor Third contributor 16 18 17 20

37 TrueAllele computes genotypes
For each contributor, at every locus Allele pair Probability 16, 18 14, 18 13, 18 18, 20 17, 18 65% 12% 10% 8% 4%

38 TrueAllele match answers
log(LR) Suspect 1 Suspect 2 Suspect 3 Suspect 4 Suspect 5 1. Gun 4 1. Hat 3 2. Safe 2. Phone 3. Counter 6 3. Safe 4. Keys 4. Tape 5. Hat 1 5. Hat 2 5. Overalls 11 5. Shirt

39 DNA mapping the crime scene
Suspects: S1, S2, S3, S4, S5 Market • hat 1 • hat 2 • overalls • shirt Food mart • gun • hat Jewelry • counter • safe Convenience • keys • tape Hardware • safe • phone

40 Computer Interpretation of Quantitative DNA Evidence
People of California v. Charles Lewis Lawton and Dupree Donyell Langston January, 2013 Bakersfield, CA Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA Cybergenetics © Cybergenetics ©

41 Evidence genotype Objective genotype determined solely from the DNA data. Never sees a reference. 51% 20% 1% 3% 2% 2% 3% 1% 2% 3% 1% 3% 1% 1% 1% 1% 1% 1% 1%

42 DNA match information How much more does the suspect match the evidence than a random person? 8x 51% Prob(evidence match) Prob(coincidental match) 6%

43 Match information at 15 loci

44 Is the suspect in the evidence?
A match between the front counter and Dupree Langston is: 553 million times more probable than a coincidental match to an unrelated Black person 731 million times more probable than a coincidental match to an unrelated Caucasian person 208 million times more probable than a coincidental match to an unrelated Hispanic person

45 Bakersfield, CA: January, 2013
• Pretrial admissibility hearing • TrueAllele admitted into evidence • DNA expert match testimony • Dupree Langston was convicted • Facing sentence of 70 years in prison

46

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