DNA evidence is often associated with exoneration of death-row inmates who shouldn't have been convicted in the first place. But DNA evidence can conceivably apply to most any type of criminal charge - not only violent crimes.

A key question, however, is what rights law enforcement officers have to obtain that evidence from people. Under what circumstances can someone simply refuse to give a DNA sample? Conversely, are there circumstances under which someone must give that sample?

Someone who has no discernable connection to a crime, who is just walking down the street, does not have to give a DNA sample, even if a police officer asks for it. On the other end of the spectrum, a prison inmate who has already been convicted of a felony does not have the right to refuse to give such a sample.

So when, during the criminal justice process, does the right to refuse to give a DNA sample get called into question? After all, the Fourth Amendment protection against unreasonable searches and seizures still exists.

In addressing this issue, courts have used the concept of a "continuum of privacy." A 3-judge panel of the U.S. Court of Appeals for the Ninth Circuit has heard oral arguments in a case challenging a California law that allows DNA testing as soon as someone is arrested on felony charges.

This fall, all of the Ninth Circuit judges - not only a 3-judge panel - will consider the case. It has important implications for anyone in need of a criminal defense.

It's important to reminder that many arrests do not end in convictions. In fact, in California, for felonies, only about half of arrests result in convictions.

DNA evidence is inherently personal. After all, it consists of the very cells from people's bodies. The courts should therefore take Fourth Amendment privacy protections seriously as they consider the proper role of DNA evidence in criminal cases.

Source: "When is it OK to Take People's DNA Without Their Consent?" the Atlantic, 8-11-11