Cybergenetics © 2007-2014 1

Revolutionising DNA analysis in major crime investigations

The Investigator Conferences Green Park Conference Centre

May, 2014 Aylesbury, Buckinghamshire

Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA

Cybergenetics © 2003-2014

Commonwealth v. Lyons homicide: DNA mixture evidence

Victim's blood spatter pulsating spray from

severed carotid artery

75% victim 25% other

Cybergenetics © 2007-2014 2

DNA molecule

Copy DNA

Copy intact DNA

Normal DNA signal

Cybergenetics © 2007-2014 3

Degraded DNA

Can’t copy broken DNA

Longer molecules copy less With degradation, a longer DNA molecule has a greater chance of having a break

DNA decay curve

DNA size

Obs

erve

d D

NA

With degradation, a longer DNA molecule makes fewer DNA copies

Cybergenetics © 2007-2014 4

Degraded DNA signal

Degraded DNA Mixture

Degraded other DNA

Victim DNA

Match statistic comparison

Human Computer

42,000 9,500,000,000,000

Cybergenetics © 2007-2014 5

Computer Interpretation of Quantitative DNA Evidence

Commonwealth v. Lyons June, 2011

Reading, PA

Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PA

Cybergenetics © 2003-2011

DNA evidence interpretation Evidence

item Evidence

data Lab Infer

10 11 12

Evidence genotype

Known genotype

10, 12 @ 50% 11, 12 @ 30% 12, 12 @ 20%

10, 12

Compare

Computers can use all the data Quantitative peak heights at locus D8S1179

victim

other

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People may use less of the data

Over threshold, peaks become allele events.

Under threshold, alleles vanish.

All-or-none allele peaks; ignore victim genotype

Threshold

How the computer thinks Consider every possible genotype solution

victim other

Explain the peak pattern Better explanation

gives a higher probability

Evidence genotypes victim other

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DNA match information

Probability(evidence match) Probability(coincidental match)

How much more does the suspect match the evidence than a random person?

6x

Is the suspect in the evidence? A match between the suspect and the evidence

is 9.46 trillion times more probable than coincidence.

Yes, with a reasonable degree of scientific certainty, evidence item Q9 contains DNA

from the genotype of suspect item K2.

Is the victim in the evidence? A match between the victim and the evidence

is 1.27 quintillion times more probable than coincidence.

Yes, with a reasonable degree of scientific certainty, evidence item Q9 contains DNA

from the genotype of victim item K1.

Cybergenetics © 2007-2014 8

Getting Started http://www.cybgen.com/support

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