Familial Identification: Population Structure and Relationship Distinguishability

Abstract

With the expansion of offender/arrestee DNA profile databases, genetic forensic identification has become commonplace in the United States criminal justice system. Implementation of familial searching has been proposed to extend forensic identification to family members of individuals with profiles in offender/arrestee DNA databases. In familial searching, a partial genetic profile match between a database entrant and a crime scene sample is used to implicate genetic relatives of the database entrant as potential sources of the crime scene sample. In addition to concerns regarding civil liberties, familial searching poses unanswered statistical questions. In this study, we define confidence intervals on estimated likelihood ratios for familial identification. Using these confidence intervals, we consider familial searching in a structured population. We show that relatives and unrelated individuals from population samples with lower gene diversity over the loci considered are less distinguishable. We also consider cases where the most appropriate population sample for individuals considered is unknown. We find that as a less appropriate population sample, and thus allele frequency distribution, is assumed, relatives and unrelated individuals become more difficult to distinguish. In addition, we show that relationship distinguishability increases with the number of markers considered, but decreases for more distant genetic familial relationships. All of these results indicate that caution is warranted in the application of familial searching in structured populations, such as in the United States.

Identification of Pedigree Relationship from Genome Sharing

“…Courts would assume this to be defined by pedigree. Another situation would be in identification of individuals in forensic cases, for example, in identifying a body or a body part in a disaster zone, or in familial searching for relatives of an offender already in the database (Rohlfs et al 2012). In studies of natural populations, pedigree construction is an important component in determining breeding structure and estimation of genetic parameters (Blouin 2003; Pemberton 2008).…”

Genetic prediction of complex traits: integrating infinitesimal and marked genetic effects

“…In some situations, it may possible to impute missing data. Also, if genealogy is unknown and if all individuals are in the genotyped sample, parent-progeny pairs can be easily identified using DNA data (Rohlfs et al 2012). However, to cover many variable situations in real life, it should be necessary to expand model [7] to include heterogeneous variances where mendelian sampling is observed for some individuals but it remains a random value for individuals without genotyped parents.…”

Probabilistic Strategies for Familial DNA Searching

“…Recently, the way that population substructure affects familial searching has also been investigated in Rohlfs et al . () and Ge and Budowle (), primarily focusing on populations that are mostly relevant for the US databases.…”