Cybergenetics Webinar January, 2015 Mark W Perlin, PhD, MD, PhD
Cybergenetics, Pittsburgh, PA Cybergenetics 2003-2015 How
TrueAllele Works (Part 4) Genotype Database and DNA Investigation
Slide 2 DNA evidence Evidence Crime scene Reference Possible
suspect Match genotype value x Single source items, from one
individual Slide 3 DNA database Evidence Genotype database Crime
scene Reference Genotype database Possible suspect Upload Match
Upload Gill P, Werrett D. Interpretation of DNA profiles using a
computerised database. Electrophoresis. 1990;11:444-8. Slide 4 DNA
mixtures eye of newt toe of frog Double, double toil and trouble
Slide 5 Allele database is broken Evidence Allele database
Reference Allele database Crime scene Possible suspect Upload Match
Upload Unseparated mixtures Slide 6 Allele database non-specificity
spuriously hit fraction of database M.W. Perlin, "Investigative DNA
databases that preserve identification information", American
Academy of Forensic Sciences 64th Annual Meeting, Atlanta, GA, Feb
2012. Slide 7 Genotype separation X1X1 X2X2 X3X3 contributor
genotypes posterior probability Slide 8 Genotype combination
likelihood ratio gives match information posterior Qposterior S
prior Slide 9 Genotype paradigm 1 st separate mixtures into
genotypes 2 nd combine genotypes into match statistics Slide 10
Genotype database Evidence Genotype database Reference Genotype
database + Crime scene Possible suspect Upload Match Upload
Separated genotypes LR Slide 11 Accurate match results
01020-30-20-10 +15-22 LR information from separated genotypes
sensitivity (true +) specificity (true ) M.W. Perlin,
"Investigative DNA databases that preserve identification
information", American Academy of Forensic Sciences 64th Annual
Meeting, Atlanta, GA, Feb 2012. Slide 12 Evidence-to-evidence
database Genotype database + Crime scene 1 Crime scene 2 Upload
Match Upload Separated genotypes Evidence + Separated genotypes
Slide 13 Quality assurance database Evidence Genotype database
Personnel Genotype database + Crime scene Lab & police Upload
Match Upload Separated genotypes Slide 14 Southampton rapist
Stranger rape on New Year's Eve Slide 15 DNA rape kit report The
DNA profile contained limited information. A speculative search was
done of the National DNA Database. The search found 13 profiles, 1
in the Hampshire area. Due to the low level and incomplete nature
of the DNA profile, it is not suitable for routine statistical
evaluation. A trace amount of semen detected on vaginal swabs was
submitted for DNA profiling Slide 16 Proper modeling uses all the
data Quantitative peak heights at locus D21S11 Slide 17
Alternatives use less of the data Threshold Over threshold, peaks
are labeled as allele events All-or-none allele peaks, each given
equal status Under threshold, alleles vanish Slide 18 How the
computer thinks Consider every possible genotype solution Explain
the peak pattern Better explanation has a higher likelihood One
person's allele pair Another person's allele pair Slide 19
Objective genotype determined solely from the DNA data. Never sees
a comparison reference. Separated evidence genotype 12% 13% 14% 2%
12% 4% 21% 2% one contributor, at one locus Slide 20 DNA match
information Prob(evidence match) Prob(coincidental match) How much
more does the suspect match the evidence than a random person? 5x
21% 4% Slide 21 Match information at 10 loci Slide 22 Is the
suspect in the evidence? A match between the vaginal swabs and
Stuart Ashley Burton is 17 thousand times more probable than
coincidence. Slide 23 Separating database hits Burton Other 40
log(LR) Slide 24 Non-contributor distribution Mean = -2.7 Stdev =
1.5 log(LR) Slide 25 Separating hits statistically non-contributor
distribution 1 in a million 1 in a thousand Burton Other Slide 26
DNA leads to conviction Mr. Burton pleaded guilty to the rape
committed on January 1, 2014. He was sentenced to 12 years in
prison. Defendant also convicted of having sex with 13 year old
girl Slide 27 Familial search child father X C + Separated evidence
genotypes Match Relatives of reference genotypes Slide 28 Missing
persons Genotypes inferred from reference relatives person XS FM
C1C2C3 + Separated evidence genotypes Match Slide 29 Mass disasters
Kinship genotypes X FM Victim remains genotypes Match + Personal
effects genotypes Slide 30 Database-driven workflow Upload plates
of EPG data files Ask computer batched questions Computer gives
genotype answers Database match directs analysis Perlin, M.W. and
Miller, K. W. P. Kern County resolves the DNA mixture crisis.
Forensic Magazine, 11(4):8-12, 2014. Slide 31 Genotype vs allele
database AttributeGenotypeAllele Mixturesseparatedthresholds
Upload100%10% Recordsprobabilitylist Comparesgenotypesdata
Comparisonlikelihood ratioinclusion Informationpreservesdiscards
Outputmatchesleads Genetic locifewmany ($) False hitsfewmany ($)
Missed hitsfewmany ($) Slide 32 How TrueAllele Works
[email protected]
http://www.cybgen.com/information/webinar/page.shtml Part 1,
16-Oct-2014 Genotype modeling and the likelihood ratio Part 2,
20-Nov-2014 Degraded DNA and allele dropout Part 3, 18-Dec-2014
Kinship, paternity and missing persons Part 4, 14-Jan-2015 Genotype
database and DNA investigation
