Challenging DNA Evidence The Fifth Judicial District of Pennsylvania Criminal Division February,...
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Challenging DNA Evidence The Fifth Judicial District of Pennsylvania The Fifth Judicial District of Pennsylvania Criminal Division Criminal Division February, 2015 February, 2015 Pittsburgh, PA Pittsburgh, PA Mark W Perlin, PhD, MD, PhD Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA Cybergenetics, Pittsburgh, PA Cybergenetics © 2003-2015 Cybergenetics © 2003-2015
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Transcript of Challenging DNA Evidence The Fifth Judicial District of Pennsylvania Criminal Division February,...
Challenging DNA Evidence
The Fifth Judicial District of PennsylvaniaThe Fifth Judicial District of PennsylvaniaCriminal DivisionCriminal DivisionFebruary, 2015February, 2015Pittsburgh, PAPittsburgh, PA
Mark W Perlin, PhD, MD, PhDMark W Perlin, PhD, MD, PhDCybergenetics, Pittsburgh, PACybergenetics, Pittsburgh, PA
Cybergenetics © 2003-2015Cybergenetics © 2003-2015
National Academy of Sciences
Among existing forensic methods, only nuclear DNA analysis has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between an evidentiary sample and a specific individual or source.
However, ... there may be problems ... with how the DNA was ... interpreted, such as when there are mixed samples
"Strengthening Forensic Science" (2009), page 100.
DNA biology
Locus
Chromosome
Nucleus
Cell
Short tandem repeat
Take me out to the ball gametake me out with the crowdbuy me some peanuts and Cracker JackI don't care if I never get backlet me root root root root root root root root root root for the home team,if they don't win, it's a shamefor it's one, two, three strikes, you're outat the old ball game
"root" repeated 10 times, soallele length is 10 repeats
23 volumes in cell'sDNA encyclopedia
DNA locus paragraph
DNA genotype
10, 121 2 3 4 5 6 7 8
ACGT
1 2 3 4 5
A genetic locus has two DNA sentences,
one from each parent.
locus
Many alleles allow formany many allele pairs.
A person's genotype is relatively unique.
motherallele
fatherallele
repeated word
An allele is the numberof repeated words.
A genotype at a locusis a pair of alleles.
9 10
6 7 8 9101112
Simple DNA evidenceEvidence
itemEvidence
data
Lab Infer
10 11 12
Evidence genotype
10, 12
DNA fromone person
DNA match statisticEvidence
itemEvidence
data
Lab Infer
10 11 12
Evidence genotype
Known genotype
10, 12
10, 12
CompareDNA from
one person
1
Prob(coincidental match)
DNA mixture
eye of newt toe of frog
Double, double toil and troubleDouble, double toil and trouble
DNA mixture interpretationEvidence
itemEvidence
data
Lab Separate
10 11 12
Evidencegenotypes
DNA fromtwo people
10, 11 @ 20%11, 11 @ 30%11, 12 @ 50%
+
10, 12
DNA match statisticEvidence
itemEvidence
data
Lab
10 11 12
Contributor genotype
Known genotype
10, 11 @ 20%11, 11 @ 30%11, 12 @ 50%
11, 12
CompareDNA fromtwo people
Prob(evidence match)
Prob(coincidental match)
Separate
