Second Of A Three-Part Series
By John Riley. Originally printed in 2004 and reposted with permission from Crime, Justice and America magazine.
The importance of DNA (deoxyribonucleic acid) in law enforcement has grown since the use was discovered in 1985. Everyone is made of cells that contain DNA (among other things). But DNA gives us our unique characteristics, and a genetic blueprint specific to each individual.
Expert Opinions Differ
Harlan Levy was an assistant district attorney in New York when he first recognized the value of DNA’s duel identity — a potential witness for the defense and for the prosecution, in cases of violent crimes.
In a book Levy wrote on the emerging DNA technology and its potential in investigating violent crimes, he said the power of DNA to identify a suspect — or to disprove an identity — promotes “a more just society, both by making punishment of the guilty more likely and by assuring exoneration of the innocent.”
Levy’s book And the Blood Cried Out: A Prosecutor’s Spellbinding Account of DNA’s Power to Free or Convict (Basic Books; 1996; 224 pages), chronicles the development of DNA as one of the greatest forensic tools developed in the twentieth century. The title refers to the biblical story where God identifies Cain as the slayer of his brother, Abel, by saying, “Hark, your brother’s blood cries out to me from the ground.”
Dr. Eric Lander, speaking in 1992 at the University of California San Francisco’s symposium, Winding Your Way Through DNA, explained some of the technology in DNA testing, and also some of the shortcomings of the relatively new forensic tool. Lander is a professor in the Department of Biology at MIT and director of the Whitehead Institute Center for Genomic Research.
“DNA gives us rich results, and just as detailed as a fingerprint — in principle,” Lander said. There are several basic steps to acquiring the DNA fingerprint. The general procedure includes:
- Isolating the DNA from an evidence sample. The DNA may from blood, saliva, or semen from any surface. These can include genital, vaginal, or cervical samples collected on swabs or gauze; rectal/anal swabs; penile swabs; pieces of tissue or skin; fingernails; plucked and shed hairs; and skin cells on drinking vessels, clothing, bedding, cigarette butts, toothbrushes, hairs in razors and hairbrushes, as well as discarded facial tissues or handkerchiefs.
- Testing the DNA.
- Comparing and interpreting the test results to determine whether the known individual is or is not the source of the DNA.
Lander explained that strings of DNA taken from such specimens as saliva, skin, blood, hair, or semen may contain billions of sequential genetic letters (there are four DNA molecules that have been given names abbreviated A, T, C and G). It would be an overwhelming and unnecessary task to read them all.
“What is done instead is that a very small handful of sites of variation are examined,” he explained.
“…one picks enough sites of variation to be able to have enough markers of difference.”
“At least in the forensic applications commonly done today, people don’t actually read out the sequence. For economic reasons, for being able to do this more quickly and more cheaply, they look instead at regions that have spelling differences that are due to repetitions of some sequence.”
Lander said blind acceptance of DNA evidence is dangerous. “DNA evidence is rapidly becoming, in principle, an irrefutable proof of identification. But of course, nothing is ever so simple…” he said. “It’s not enough to say it’s okay in principle — it must be okay in practice as well. And although everyone agrees that this is a spectacular technology, controversies have erupted in the scientific community from time to time over whether it’s really being done right. Fights erupt over DNA fingerprinting because it’s such an important technology.
“What have these fights been about? They have not been about how to do it in principle. They have been about how to do it in practice, and how well-regulated the practice is.”
Practices Vary
Handling the DNA evidence once it has been collected is one of the practices referred to by Lander. Improperly handling of the DNA could lead to contamination, which was a major issue in the 1995 murder trial of O.J. Simpson — charged with the June 12, 1994 stabbing deaths in Los Angeles of his estranged wife Nicole Brown Simpson and Ronald Goldman.
Prosecutors claimed Simpson left a trail of his own blood at the murder scene, and they used DNA from the blood to make the identification. Defense attorneys argued the blood was contaminated by improper handling and storage, and that the DNA was therefore contaminated. (They also argued the blood had been planted by police.) When Simpson was found not guilty, there was concern among some in the community of forensic experts that DNA’s credibility would be damaged, perhaps beyond repair.
However, in Levy’s book he pointed out that Simpson’s defense team did not attack the integrity of DNA typing itself, but rather successfully created doubt by raising questions of police misconduct and poor evidence handling.
Lander said during his San Francisco speech, “Obviously, a technology that is so powerful and that is [so] sensitive must be used even more carefully, since you can imagine that if I sneeze on something, my DNA is there, too. And so there is tremendous need to avoid contamination. Whether laboratory practice is up to that — the proficiency tests have to be put in place to guarantee that they’re up to that.”
Opinions On Privacy Issues
The creation of DNA databases is also a point of controversy. “There has been discussion about creating national databases of everyone’s DNA type,” Lander said. “That way, when a rape is committed, there’s no need to find a suspect. You take the segment sample and get its DNA pattern, and compare it to a database of everyone’s DNA pattern and find out whose it was.
“There are many people who feel understandably uncomfortable about such a national database. So legislatures have instead decided in some states to set these up, not for all citizens, but for only those convicted of, say, sex offenses, and other states for those convicted of any felony.
“There is a lively controversy over what sorts of databases should be set up, and there are those who say — why should it matter? Why should you care if you’re in a database? After all, if you’re innocent, there’s no chance the technology will do you any harm.”
The Truth Is Out There
In a 1999 review of Harlan Levy’s book on DNA, Clay Strange (an assistant district attorney in Travis County, Texas) wrote that the former Manhattan prosecutor “came to realize… that although DNA was unparalleled in the determination of the truth, the truth wasn’t necessarily a product the criminal courts were interested in.
“He became disillusioned with most judges’ traditional view of trial `as a process, pursuant to the rules of evidence, to determine whether guilt has been proven beyond a reasonable doubt.’” According to Strange, the overwhelming desire to preserve process over truth led to the “DNA admissibility wars” of the late 1980s and early ‘90s.
Levy’s book spotlights the case that helped ignite the war — that of murder suspect Joseph Castro. Until Castro’s case hit the courtroom, DNA was on a fast track to become an unquestionable arbiter of truth. In his review of Levy’s book, Strange relates that Castro was charged with the stabbing death of a young woman and her two-year-old daughter in the Bronx, N.Y. in 1987. Blood on Castro’s watchband was the principal piece of evidence. Prosecutors believed it belonged to one of the victims.
“What followed was to be the only real derailment of an otherwise generally flawless progress toward widespread acceptance of and reliance on … DNA typing,” Strange wrote. Dr. Richard Roberts testified for the state as an expert witness on DNA in the Castro trial. Roberts was an associate of James Watson, co-discoverer of the double-helix structure of the DNA molecule. Lander was among the witnesses for the defense who challenged the matching criteria used by the DNA lab.
The court eventually excluded the DNA evidence because of the way it was collected and stored — a severe public relations blow for the new technology that many had thought to be infallible.
But, according to Levy, the results of the case overshadowed the fact that the scientific validity of DNA was not actually challenged, but rather the techniques in gathering and preserving the evidence. And, even though the DNA evidence was tossed out as being too inconclusive, Castro pled guilty.
The Record Is Mixed
Levy also noted in his book that the Castro case was not the only setback. In 1992, the National Academy of Sciences National Research Council issued a report that endorsed DNA technology, but questioned the statistics for the probability of DNA matches.
In his review of the book, Strange wrote, “The report attempted a compromise known as the `ceiling principle,’ which sought to resolve perceived statistical difficulties within certain population subgroups. The proposed solution created a firestorm in the forensic DNA community. The FBI and most population geneticists attacked the concept [of the ceiling principle] as pure politics and bad science.” The upshot, said Strange, was a second NRC report that discarded the so-called ceiling principle and re-instituted the statistical method previously used.
Former Attorney General Janet Reno was more enthusiastic, but even she expressed some reservations. In 1996, she created the National Commission on the Future of DNA Evidence. “The development of DNA technology has done so much in these ten years to improve our criminal justice system,” Reno told the commission at its opening session. “I remember as a prosecutor in Miami beginning to understand absolutely the awesomeness of it all and not quite able to get my hands around it. I realized how long I had been in Washington by recognizing that eight of these ten years have been spent here watching [DNA as an investigative tool] just mushroom across the nation.
“We have seen it go from a technology used by a few prosecutors in a few jurisdictions to a technology now accepted in every court in the United States. We now have legislation in every state creating DNA databases of our most violent offenders.
“We can now identify suspects in cases where no other evidence exists but the saliva or the skin cells. We can now use DNA to solve cases that are 10, 20, or 30 years old; and we can identify a suspect in a crime from Florida from his prior conviction in the state of Illinois…
“DNA evidence lies as only potential until it is properly identified, collected, stored, and analyzed; and we must make sure that we remember it is human beings that are doing that. We can never say that it will be technology that solves the problem. It will always be humans interpreting the evidence, using the evidence, collecting the evidence, maintaining the evidence that will insure ultimate success.”
The Future Is Now
Harlan Levy saw the potential for not only using DNA to identify potential crime suspects, but as a way of correcting past mistakes made by human error in the prosecution of innocent people.
As both Levy and Attorney General Reno noted, if DNA evidence is kept properly, it can be tested accurately years later — a fact that has given hope to many inmates who were wrongly convicted of crimes.
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