A investigation technique wherein a large section of a population is asked or forced to submit to DNA fingerprinting, usually in an effort to solve a violent crime. While all dragnets seem to clash with the concept innocent until proven guilty and are on questionable legal footing concerning the Fourth and Fifth Amendments, DNA dragnets raise further issues of bioethics and genetic privacy. These can be demonstrated by analysing an ongoing example of one.

As of this writing, a comprehensive collection of DNA samples from the men of Truro, Massachusetts is underway in an effort to solve a three-year-old murder case. Christa Worthington was stabbed to death in her home on January 6, 2002. With no remaining suspects after three years, state and local police are attempting to match the DNA of semen found on Worthington’s body to one of the 790 men that live in the tiny Cape Cod town year-round.

This DNA dragnet hopes to utilize DNA fingerprinting in true crime drama fashion; the miracle of science used to crack an otherwise uncrackable case. Even understanding that the male who deposited the original DNA evidence might have nothing to do with Worthington's murderer, the officials are desperate for a lead. Large scale sweeps of this sort have been conducted in the U.S. a handful of times, and are more common in Europe, but it remains to be seen whether they are any more effective than traditional police work.

DNA fingerprinting has been used very effectively when there are a small number of suspects. However, when the suspects are everybody capable of producing semen in a idyllic American town things tend to get a little sticky. The precedent setting case occurred in Britain in 1987, and is well described in Vorbis's DNA fingerprinting writeup. That dragnet aimed to collect 5,000 samples; the adult male population of three neighboring towns. In the end, the killer, Colin Pitchfork, was discovered not by his DNA sample, but rather by his attempt to avoid providing one. This is an important facet to keep in mind when thinking about the ethical implications of this investigation technique. We'll get back to that in a moment.

The overall response to the Truro dragnet has been compliance and support. However, some of the residents have already refused to submit to the testing. Unsurprisingly, there have also been several complaints to the American Civil Liberties Union. The Massachusetts branch of the ACLU has called for an end to the sweep, claiming that although the tests are ostensibly voluntary and thus not a violation of constitutional protections against unreasonable searches and seizures, the implications of refusing to submit DNA samples in this context are coercive. Police have recorded the identities and license plate numbers of men who refuse the test, which could mean that refusing is tantamount to becoming a suspect.

Truro's citizens and the ACLU are concerned with issues of privacy, as well. The police claim that DNA samples will be destroyed after it is proven they do not match the evidence initially collected, though many are skeptical. Participants in other dragnets in the United States have had sued to ensure their samples were purged from databases, but were met with very limited success. There are no official guidelines for conducting such searches; participants and protesters alike are concerned that the DNA collected could be sold or otherwise given to interested parties, such as other criminal databases or insurance providers. Genetic discrimination is a frightening prospect that is quickly becoming more and more realistic.

There are also logistical concerns with these kinds of sweeps. For the cost (an estimated $80,000) and the time it will take to process all of the collected samples (the DNA testing of the few original suspects took several months), it is unclear if the dragnet will be any more effective than traditional, less intrusive police work. Critics of the technique argue that such dragnets have been showed to be unreliable and fail far more often than they succeed. A Baton Rouge, Louisiana murder case that employed a DNA dragnet targeting about 1,000 white males proved to be moot when a black man was convicted. Recent dragnets in Ann Arbor, Michigan, Miami, Florida and Omaha, Nebraska were also met with similar results. In the U.K., where many more DNA dragnets have been conducted, only 61 of the 292 sweeps have come up with significant results.

This brings us back to the the Pitchfork case. While two-dimensional electrophoresis was necessary of linking Mr. Pitchfork to the two crimes, his DNA was not caught by the proverbial net. He had convinced someone else to take the blood test in his stead, and it was only after a third-party tipped off the police to this fact that Pitchfork was directly tested and arrested. If the Pitchfork model is to be considered standard operating procedure for success in U.S. DNA dragnets, it seems that they are clearly in violation of the Fourth and Fifth amendments. Specifically, it pits the two Amendments against one another. When asked to voluntary sample under a DNA dragnet, one must abdicate their Fourth Amendment right to refuse such a search, or else abdicate their Fifth Amendment right from potentially incriminating themselves.

With the overwhelming support and passage of Proposition 69 in California last November, which allows police to take DNA samples from all arrestees, it seems that the number, and acceptance, of DNA dragnets like Truro’s is only going to rise. Although the prospect of conclusively solving violent crimes is very appealing, it will take the combined effort of civil libertarians and responsible scientists to ensure that these dragnets do not become an abusive fixture of the U.S. criminal justice system.