Criminalists, serologists, district attorneys, cops and even a few defense attorneys gathered together for the Second National Conference on the Future of DNA: Implications for the Criminal Justice System. DNA is on the cutting edge of forensic science, a genetic fingerprint that can help identify or rule out suspects in a violent crime. And even in the staid atmosphere of the convention, where the traditional combatants met without the pressures of court, there was tension in the air. While the science behind DNA is largely accepted, it provides such decisive evidence of guilt or innocence that it is still surrounded by controversy. Defense attorneys usually hate it, and will do anything to have DNA evidence ruled inadmissible, while prosecutors build entire cases around the identification of body fluids left at the scene of a crime.
"Defense attorneys use DNA evidence wholeheartedly ... when the DNA evidence will help to exonerate and rule out their clients," said Ken Konzak, assistant lab director for the California Department of Justice, Division of Forensic Services. "It is only when the evidence will tend to convict that it is suddenly 'unreliable science.'" It is, perhaps, not surprising that this conflict rose quickly to the surface when a defense attorney and a prosecutor attempted to share a podium at the DNA convention.
Traditional Enemies
When Jim Sherriff, Jr., a Sacramento-based defense attorney and founder of the DNA Litigation Project, took the stage, he quickly put the audience -- primarily forensic scientists -- at ease with his complete support for DNA science. "As a defense attorney, it is my job to make it as difficult as legally and ethically possible for the prosecution to meet its burden of proof. But the truth is that DNA is great evidence. In fact, DNA analysis is creating a revolution in the evidentiary process. The theory is sound and the evidence is better -- more accurate -- than having an eyewitness, though not quite as good as fingerprinting," said Sherriff.
Case closed, it seemed, until Geoff Lauter, a Sacramento County assistant district attorney, followed Sherriff to the podium. "That sounds great, but I have found myself in an admissibility hearing with Sherriff and I don't remember him saying anything like this before," said Lauter. "When he says the role of the defense attorney is to be the best advocate for their client they can legally and ethically be, I wonder if that includes creating confusion and distracting the eyes of the judge and jury from the truth. Even here, right now, while I respect Jim's abilities, I have to remind him that in our case, he didn't come in and say DNA was good evidence or solid science, but instead said it wasn't proven or accepted and actually called it 'a bunch of hooey.' I wonder, what has changed so suddenly?"
DNA analysis is used in the investigation of approximately 10,000 criminal cases -- 75 percent of which involve sexual assault -- and about 130,000 civil paternity cases each year. As DNA science has become more refined and been given broad support by members of the scientific community, DNA evidence is being accepted in the courtroom to a degree not previously seen. While only five years ago law enforcement officials found themselves fighting to bring DNA into the courtroom, there are now three states -- Nevada, Oklahoma and Tennessee -- where the legislature has specifically passed laws stating DNA evidence can be used in the courtroom, and only four states -- Maine, North Dakota, Rhode Island and Utah -- where it is commonly excluded from the courtroom. In the remaining 43 states, DNA evidence is routinely allowed into courtroom trials, though often only after costly and contentious admissibility hearings.
"The reality is that most defendants that go to trial in the United States are factually guilty, and defense attorneys know that a properly conducted DNA test is [most often] going to confirm guilt," said Professor Edward J. Imwinkelreid, a DNA expert who teaches law at the University of California at Davis. "That is why we have to face these long admissibility hearings, which can sometimes last longer than the actual trial. The last thing the defense wants is a properly conducted DNA test. So they fight admissibility hard."
They put up that resistance by calling into question lab procedures that may have allowed contamination and the population statistics that give DNA evidence its meaning. When a forensic scientist picks up a pair of underwear at a rape scene, he or she is hoping that the attacker's sperm will be on the cloth. When it is, great care must be taken to follow correct procedures, as that will most often be the defense's line of attack.
The Most Powerful Tool
When a suspect is apprehended, his own blood is sampled, a DNA analysis is done and compared with the DNA "fingerprint" collected at the crime scene. "About 95 percent of our DNA chain is the same as everyone else's," explained DOJ's Konzak.
"What we look for are the places where the chain is commonly unique. At each spot where the chain is unique, we can compare the evidence sample to a suspect's sample and make a statistical assessment of how likely it is that more than one individual has that unique gene trait. Since we usually look at anywhere from four to six sites on the DNA chain, we can establish statistical probabilities that leave little room for doubt. When you can say only one in 10 billion individuals is likely to have this same DNA print, and there are only 250 million people in the whole United States, you don't need a lot more evidence of guilt."
In fact, it is not uncommon for murder defendants to admit their guilt when faced with such conclusive evidence, or rapists to quickly change their defense from outright denial to a claim that sex was consensual. To many in law enforcement, DNA evidence is considered the most powerful tool to come along in a century or more. Industry experts expect more states to approve legislation mandating the admissibility of DNA and fewer courtrooms to resist that admission.
"The only battles left are over techniques. The technology is accepted, and soon there will be no one left to challenge it," said Imwinkelreid. "But, while we have powerful technologies, and DNA is one of the most powerful we have, we still have human beings who are underworked and underpaid handling the testing. Defense attorneys will always be able to make a case for the possibility of mistakes being made."
Ray Dussault is a Sacramento, Calif.-based freelance writer. E-mail:
There are roughly 100 trillion cells in an adult human body, and most of those cells hold threadlike bundles of chromosomes that contain all the instructions needed to make a human BODY. Within the chromosomes are genes, the base units that contribute to what we generally refer to as heredity. If you inherited your mother's blue eyes or father's brown hair, it came in the coding of these genes.
Of course, even genes are made of something else, and that something is deoxyribonucleic acid -- DNA. DNA is the master molecule, and each DNA consists of a long string of repeating units called nucleotides. The four nucleotides in the body are adenine (A), cytosine (C), guanine (G) and thymine (T). Just as we can form millions of words by different arrangements of a 26-letter alphabet, DNA coding gives its message to the body through the order in which these base nucleotides are strung together. Since each of us is generally similar physically, the vast majority of DNA coding is the same from person to person, but DNA identification works by examining those points in the DNA strand that give us our individual characteristics.
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