Transcript Forensic statistics: extreme numbers and the Birthday Problem

Forensic statistics: extreme
numbers and the Birthday
Problem
Bruce Weir
[email protected]
JonBenet Ramsey
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DNA tests clear JonBenet Ramsey's family of her 1996 killing
Results point to 'unexplained third party,' prosecutor says
Last Updated: Wednesday, July 9, 2008 | 5:47 PM ET
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CBC News
Prosecutors in Colorado have cleared the parents of JonBenet Ramsey, a
child beauty queen shown in this undated photo, of involvement in her
unsolved homicide in 1996. (Denver Post/Associated Press)
The parents of American child beauty queen JonBenet Ramsey have been
cleared of involvement in her unsolved 1996 killing by new DNA tests,
prosecutors in Colorado said Wednesday.
The tests point to an "unexplained third party," Boulder County district
attorney Mary Lacy said.
Prosecutors don't consider any member of the Ramsey family to be a
suspect, Lacy said as she released a copy of a letter to the Ramseys that
also contained an apology for the failure to find the killer.
"We intend in the future to treat you as the victims of this crime, with the
sympathy due you because of the horrific loss you suffered," the letter says.
Starr Report
World Trade Center
Bertillonage
Bertillonage
Fingerprints
Galton’s Fingerprints
Fingerprint Extreme Numbers
Uniqueness of Fingerprints
People v. Collins
Gregor Mendel
Blood Groups
Blood Group Exclusions
Blood Groups of Children
Blood Group Inclusions
Types of Polymorphism
First Immigration Case
Aronson, 2007
First Forensic Case
Single-locus Probes
Polymarker System
Simpson case Polymarker profiles
Schematic RFLP typing
Simpson Case VNTR Profiles
Snowball the Cat
Menotti-Raymond, 1997
Michaelis, Flanders & Wulff, 2008
Russian Tsar Nicholas II
Goodwin, Linacre & Hadi, 2007
Goodwin, Linacre & Hadi, 2007
Arizona Database Hits
The Birthday Problem
The Birthday Problem
Expected Arizona Matches
Familial Searching (UK)
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Britain
Times OnlineJuly 17, 2006
• Shoe rapist caught by new DNA technology
• By Andrew Norfolk
• A serial rapist who today admitted raping four
women and trying to rape two others hid more
than 100 pairs of stiletto-heeled shoes - some of
them belonging to his victims - at his workplace,
police said yesterday.
Familial Searching (US)
Familial Searching
Cold Hits
Cold Hits
there is a very high probability
that an animal has four legs
If it is an elephant
Pr(Four legs | Elephant) = 0.9999
SO!! - there is a very high
probability that an animal is an elephant
if it has four legs.
Pr(Four legs | Elephant) = 0.9999
Pr(Elephant | Four legs) = 0.9999
???
Examples about elephant’s legs may seem
easy to follow - but it’s often not so easy in
court proceedings.
Prosecutor’s Fallacy
Prosecutor’s Fallacy
Prosecutor’s Fallacy