Complexity and Social Networks Blog

Using Relatives' DNA to Identify Criminals
Potential problems and benefits identified in new research study

Genetic analysis of proliferating DNA databases maintained by the criminal justice system might enable criminals to be caught by recognizing, as their kin, those in these databases. While use of these novel methods could provide thousands of new investigative leads, they also raise challenging legal and policy questions. These findings along with discussion of the legal and policy issues are published in ScienceExpress, the advance online version of Science, on May 11, 2006.

The article is co-authored by Frederick R. Bieber, PhD, a medical geneticist at Brigham and Women’s Hospital and Associate Professor of Pathology at Harvard Medical School; Charles H. Brenner, PhD, a forensic mathematician and Visiting Scholar at the School of Public Health, University of California, Berkeley; and David Lazer, PhD, Director of the Program on Networked Governance and Associate Professor at Harvard’s Kennedy School of Government.

“We demonstrate that the kinship analysis methods routinely used for humanitarian mass disaster and missing persons identifications could also be used to identify criminals who are close relatives of those in the rapidly expanding offender DNA databases,” says Bieber.

Currently there are about 3 million individuals in offender databases around the country, largely including individuals convicted and arrested of serious crimes. The genetic profiles of these individuals are then compared to evidence of crime scene evidence, potentially linking known individuals to crime scenes. The team evaluated the potential for using these databases to link crimes to individuals related to those in the database by analyzing data on existing genetic markers used in forensics to calculate likelihood ratios (LRs) of potential parent/child and sibling relationships between each offender in the a simulated database and a crime scene DNA profile. They did this to assess the chance that a crime scene sample belongs to the close relative of a cataloged offender. The higher the LR is, the more likely that the crime scene DNA sample belongs to a close relative in the offender database. “The simulations illustrate that kinship searching used in conjunction with follow-up analysis, preferably using Y-chromosomal–markers, can expand the reach of the DNA databases not by handfuls, but by gross amounts,” said Brenner.

Researchers note two important caveats, however; that although unusual, a high LR may be a result of a coincidence for unrelated individuals and that a DNA match does not necessarily prove guilt.

“Kinship analysis, as with any investigative technique, may lead to the investigation of the innocent,” says Lazer. “But it would also provide decisive leads in cases that would otherwise go unsolved. Conceivably it could provide a large number of cold hits.” A cold hit refers to the chance of finding a match between a crime scene sample and someone in the offender database.

Kinship analysis would also reflect the current composition of the database. “The database is disproportionately African American, Hispanic, poor, and those who would be indirectly included through kinship analysis would reflect those disparities,” says Lazer.

Opposition to DNA databases has been in the form of protection against civil liberties, specifically privacy. However, courts thus far have ruled that public safety concerns outweigh individual privacy rights regarding offender DNA databases. Current laws, both state and federal, do not address kinship searches, probably because these strategies were not considered when the original laws were drafted.

“While it is exciting and important to acknowledge the potential value that genetic kinship analysis could have in forensic investigations, it is also necessary to take heed of the legal and policy implications,” says Bieber.

These and related issues will be discussed at a DNA Fingerprinting and Civil Liberties National Symposium being held in Boston, May 11-13, sponsored by the American Society of Law, Medicine and Ethics.