Improved DNA techniques now make it possible for law enforcement to identify an individual based on their relatives’ DNA, which greatly expands the scope of DNA databases utility and raises significant Constitutional questions

Some criminal investigations are straightforward. Some are convoluted. Some are just frustrating, as lead after lead is exhausted and discarded. Sometimes DNA evidence can be used to solve these cases. DNA evidence can be extremely effective when prepared properly due to DNA’s unique structural qualities and the ability scientifically to match these unique elements to individuals.

DNA evidence can be used to identify a suspect and provide a potentially very strong link in the chain of evidence needed to convict. It can also be just as effective in ruling out suspects who do not match DNA from a crime scene.

It has also been the most effective tool to “prove innocence” in exoneration cases, where the examination of DNA can just as authoritatively rule out individuals who had been “identified” by eyewitnesses or other less reliable means.

Blinded by science

There is, however, danger when that effectiveness overwhelms the Constitution and the Fourth Amendment’s prohibition against unreasonable searches and seizures. Given the potential accuracy of DNA matches, from a law enforcement perspective, the most efficient means of solving some crimes would involve obtaining DNA samples of everyone when they are born and inputting that into a giant database.

With that, anytime a crime occurred with DNA evidence, a sample could be run and a match found. Of course, this would be unconstitutional. Permitting the state to obtain such a sample without probable cause and a warrant would clearly be unreasonable.

But what about your relatives?

A recent innovation in the use of DNA evidence is the use of what is known as familial DNA. Because of the close genetic relationship of you to your parents or siblings, if the state has a sample of one of their DNA profiles, it may be able to use the profile to identify you by the similarity of genetic markers in that DNA to your DNA. This uses a “partial match” to identify DNA that is similar. Of course, this opens the door to the potential of more error.

This was used in California to identify the man known as the “Grim Sleeper” and in Kansas, to identify the BTK serial killer. In the later case, they used a sample obtained from his daughter’s Pap smear. In other cases, they have used DNA from a brother or son.

California authorities list seven cases where evidence obtained this way was used to prosecute other individuals. While it is effective and only has been used in a few cases, the concerns are great.

It is not fool proof

Mistakes can be made, as in the case of one man who was interrogated for hours on suspicion of being involved in a murder two decades earlier. It was only after a DNA test of his sample proved not to be a match that he was freed of suspicion. The original match was based on a DNA sample provided to an ancestry study and the data was later sold.

As more DNA is collected and available to match, the potential for errors increases. These are the types of law enforcement processes that could be subject to a great deal of abuse if they are not strictly supervised and controlled.

California and eight other states have protocols that permit the use of familial DNA, while Maryland and the District of Columbia have laws that prohibit its use. In the rest of the nation, there is no specific law or rule that controls the use of the technique. The problem in many of the states that do have policies is that the policies are often little more than administrative guidelines. Not only is there no public input into their design, but in many states, there may not even be an awareness that they exist.

Due to the large presence of minorities and people of color in many state criminal databases, there should be careful monitoring of the use of the procedure to ensure that it is not employed in a manner that exacerbates the perception in those communities that they have been targeted by the police. Unrestrained, the procedure could be used to profile and harass, further raising distrust of law enforcement among these groups.

Science must serve justice

The potential for abuse is great. The protocols should not be left to the whim of law enforcement; they should be subject to legislative hearings and be governed by legislatively enacted laws, which the courts can then enforce.

As with many issues involving forensic science, the use of familial DNA must be done properly, by trained technicians. The work should be closely scrutinized by the courts to ensure that it does not become a lazy and cheap method of “rounding up all the usual suspects” and blatantly violating the Constitution in the process.