Database SearchesDatabase 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 DNA profiles. Wiley•Ian Evett and Bruce Weir, 1998. Interpreting DNA evidence. Sinauer.

CODIS SystemCODIS System

• National DNA Index System (NDIS)

• State DNA Index System (SDIS)

• Local DNA Index System (LDIS)

Federal DNA Identification Federal DNA Identification Act of 1994Act 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”

Roadblocks to AccessRoadblocks 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.

Arizona ObservationsArizona 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 RMP’s?

Simulate an Offender PopulationSimulate an Offender Population

Using Arizona to Test the Product Using Arizona to Test the Product RuleRule

ResultsResults

• There is a narrow range of siblings required to explain these results

• Between 1000 – 3000 pairs of full sibs, and theta from 0.005 to 0.015.

• 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.