title: The effect of wild card designations and rare alleles in forensic DNA database searches.
abstract: Forensic DNA databases are powerful tools used for the identification of persons of interest in criminal investigations. Typically, they consist of two parts: (1) a database containing DNA profiles of known individuals and (2) a database of DNA profiles associated with crime scenes. The risk of adventitious or chance matches between crimes and innocent people increases as the number of profiles within a database grows and more data is shared between various forensic DNA databases, e.g. from different jurisdictions. The DNA profiles obtained from crime scenes are often partial because crime samples may be compromised in quantity or quality. When an individual's profile cannot be resolved from a DNA mixture, ambiguity is introduced. A wild card, F, may be used in place of an allele that has dropped out or when an ambiguous profile is resolved from a DNA mixture. Variant alleles that do not correspond to any marker in the allelic ladder or appear above or below the extent of the allelic ladder range are assigned the allele designation R for rare allele. R alleles are position specific with respect to the observed/unambiguous allele. The F and R designations are made when the exact genotype has not been determined. The F and R designation are treated as wild cards for searching, which results in increased chance of adventitious matches. We investigated the probability of adventitious matches given these two types of wild cards.
authors.affiliation: Department of Mathematical Sciences, Aalborg University, Fredrik Bajers Vej 7G, DK-9220 Aalborg East, Denmark. Electronic address: tvede@math.aau.dk.
authors.forename: Torben
authors.initials: T
authors.lastname: Tvedebrink
authors.affiliation: Institute of Environmental Science and Research Ltd., 120 Mt Albert Road, Auckland 1025, New Zealand. Electronic address: jo.bright@esr.cri.n.
authors.forename: Jo-Anne
authors.initials: JA
authors.lastname: Bright
authors.affiliation: Institute of Environmental Science and Research Ltd., 120 Mt Albert Road, Auckland 1025, New Zealand. Electronic address: john.buckleton@esr.cri.n.
authors.forename: John S
authors.initials: JS
authors.lastname: Buckleton
authors.affiliation: Department of Statistics, University of Auckland, 38 Princes Street, Auckland 1010, New Zealand. Electronic address: tvede@math.aau.dk.
authors.forename: James M
authors.initials: JM
authors.lastname: Curran
authors.affiliation: Section of Forensic Genetics, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Frederik V's Vej 11, DK-2100 Copenhagen East, Denmark. Electronic address: niels.morling@sund.ku.dk.
authors.forename: Niels
authors.initials: N
authors.lastname: Morling
mesh_terms: D000483:Alleles; D003415:Crime / Q000706:statistics & numerical data; D004247:DNA / Q000032:analysis / Q000235:genetics; D016172:DNA Fingerprinting / Q000379:methods*; D030561:Databases, Nucleic Acid; D053803:Forensic Genetics / Q000379:methods*; D005787:Gene Frequency; D006801:Humans; D018895:Microsatellite Repeats; D015233:Models, Statistical; D011336:Probability
chemical_list: D004247:DNA
keywords: Adventitious matches; Forensic DNA databases; Non-concordance; STR profiles