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Database Searches Evidence profiles are compared to a list of up to 3,528,903 profiles (FBI CODIS) References Balding, 2005. Weight-of- evidence for forensic.

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Presentation on theme: "Database Searches Evidence profiles are compared to a list of up to 3,528,903 profiles (FBI CODIS) References Balding, 2005. Weight-of- evidence for forensic."— Presentation transcript:

1 Database Searches Evidence profiles are compared to a list of up to 3,528,903 profiles (FBI CODIS) References Balding, Weight-of- evidence for forensic DNA profiles. Wiley Ian Evett and Bruce Weir, Interpreting DNA evidence. Sinauer.

2 CODIS System National DNA Index System (NDIS) State DNA Index System (SDIS) Local DNA Index System (LDIS)

3 Federal DNA Identification Act of 1994 the databases be (3) maintained by Federal, State, and local criminal agencies … pursuant to rules that allow disclosures of stored DNA samples and DNA analyses only – (D) if personally identifiable information is removed, for population statistics databases for identification research and protocol development purposes, or for quality control purposes

4 Roadblocks to Access (1) Release of even the numbers of matches at 9 or more loci would be in violation of the Federal DNA Identification Act or the local State equivalent. (2) Doing such searches would tie up forensic lab computers for an extraordinary amount of time and prevent important database searches. (3) Laboratory personnel do not have the technical expertise to carry out such searches. (4) Doing these searches or providing outside scientists with the genetic profiles in the database would violate the local labs memorandum of understanding with the FBI. (5) Other large databases are publicly available which scientists could use for any conceivable research. (6) Worthwhile research can not be accomplished with offender databases and thus should not be attempted.

5 Arizona Observations All possible pairs of 65,493 people were compared to each other at 13 loci There were a total of 122 pairs of people that matched 9 out of 13 loci, 20 matches at 10 loci, 1 at 11 loci and 1 at 12 loci. Can these numbers of partial matches be predicted from the standard models used for predicting RMPs?

6 Simulate an Offender Population

7 Using Arizona to Test the Product Rule

8 Results There is a narrow range of siblings required to explain these results Between 1000 – 3000 pairs of full sibs, and theta from to Less distant relatives, like parent-offspring combinations can not explain Arizona no matter how many are added or what the value of theta is. Song & Slatkin show departures from independence get worse over more loci.


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