New research published this week in PLoS Genetics ,indicates that individuals that are unrelated may be mistakenly be identified as genetic family members because of inaccurate genetic assumptions. This is of particular importance in familial searches, a new technique that extends forensic identification to family members of individuals with profiles in offender/arrestee DNA databases.
Researchers at Washington University and Berkeley in California demonstrate that the chance of false familial identification could be higher for individuals with particular genetic backgrounds, such as Asians or Native Americans in the USA.
Familial searches involve a partial genetic profile match between a database entrant and a crime scene sample to implicate genetic relatives of the database entrant as probable sources of the crime scene sample.
In traditional forensic DNA identification all genetic markers must match exactly, however, in familial searching it suffices that only a portion of genetic markers have to match in order to suggest a biological relationship. Even though this method can assist in identifying suspects who are currently not listed in databases, it is also has a higher rate of error.
Potential errors can be traced to marginal genetic differences between groups of individuals. Even though all humans share a recent common origin as well as the vast majority of their DNA, a small fraction of the genetic variation are nevertheless different in frequency amongst groups of people depending on their population history.
The statistical likelihood of an observed partial match is calculated from these population-specific frequencies and provides law enforcement with information about the strength of evidence for a genetic familial relationship.
The new study demonstrates that genetic profiles of unrelated individuals could potentially appear similar enough to closely match genetic relatives, which can lead to incorrect assumptions. Particularly in the United States, where most individuals are generally assumed to be of African American, European American, or Latino genetic ancestry, this kind of error tends to be greater for those of Asian or Native American descent.
The U.S. criminal justice system more frequently uses genetic forensic identification as the offender/arrestee DNA profile databases increases. These findings suggest treating familial searching in structured populations with caution, as in the United States. The relative impact of identifying individuals in practice will depend on the exact methods and databases used.
Written by Petra Rattue