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What is familial DNA testing & how is it used in criminal justice?

On Behalf of | Feb 2, 2017 | Criminal Defense |

DNA analysis is a sophisticated (and usually accurate) tool for solving crimes; especially sex offenses, murders and other violent crimes. If police already have a suspect, any traces of DNA left at the crime scene can be analyzed and potentially matched to samples taken from the suspect.

In cases where there is no immediate suspect, however, DNA matching is somewhat a matter of chance. Most states, including Michigan, now keep DNA databases of individuals who have been convicted of certain crimes. The logic behind criminal DNA databases is that individuals who commit serious crimes like rape and murder have likely already been identified within the criminal justice system. By checking crime scene DNA against the database, police might be able to identify a known offender.

Of course, this technique is only successful if the unknown suspect already has a criminal record that required submitting a DNA sample. If they are not in the database, it is of little help to investigators.

To combat this problem, law enforcement agencies in a number of states have begun to implement or consider a technique known as familial (DNA) searching. It essentially widens the database search to include individuals who are likely related to the person whose DNA was discovered at the crime scene. For instance, an unknown suspect may not be in the database, but perhaps his brother is.

Over the past decade, familial searching has been used more than a dozen times in cases around the United States. It is currently being considered in a rape and murder cold case in New York. There is little debate about the fact that it can provide valuable leads.

But there are also serious concerns, both ethical and practical. First of all, it casts a very wide net; one that is far wider than intended when most criminal DNA databases were created. There are concerns that such a wide search could be in violation of the Fourth Amendment’s ban on unreasonable search and seizure.

Second, no crime-fighting tool is error-proof. By expanding a DNA search to include likely family members, innocent individuals could be wrongfully implicated in crimes they had no connection to. Even in regular criminal testing of DNA, errors can and do occur. Often, they are related to evidence being tainted or mishandled in a lab environment.

There may be no easy answer to whether or not familial searches can or should be used. But it is an issue that, at the very least, requires significant thought and ethical debate.