Revolutionising DNA analysis in major crime investigations ?· Cybergenetics © 2007-2014 1 Revolutionising…

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  • 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

    Cant 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

  • Cybergenetics 2007-2014 6

    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

  • Cybergenetics 2007-2014 7

    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.

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

    Questions?

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