By Tom Interval
Clyde Charles never thought that hitchhiking on a lonely Louisiana road would lead to his imprisonment—a nightmare that would rob him of the next 18 years of his life.
But at 4:30 that March 1981 morning, as Charles returned from a night of visiting local bars, a police officer responding to a rape in an adjacent sugar-cane field spotted him.
Charles was arrested, identified, charged and ultimately convicted of aggravated rape, a charge that carries a mandatory life sentence in Louisiana. Consequently, Charles, who had no prior convictions, was sent to Louisiana State Penitentiary to live out the rest of his years.
There was, however, one major problem with the seemingly open-and-shut case: Charles was innocent.
After spending nine years in prison, Charles learned that the results of newly available DNA tests were being used as evidence to re-open previously tried cases. He spent nine more years battling state and federal officials, who denied his requests for a DNA test. Finally, in May of last year, a federal magistrate allowed for the test, which compared his genetic code with that contained in a semen sample collected at the crime scene. The test cleared him of the rape charge. Seven months later, he was released from prison.
At one time, it would have been inconceivable that a tiny speck of blood, hair or semen could mean the difference between a suspect’s conviction or release, his life or death. But thanks to current DNA identification procedures, drawn from classic life-science techniques, those specks are playing a crucial role in many trials. Increasingly, too, DNA analysis is being used to vindicate wrongly convicted people like Charles, just one of at least 64 prisoners in the United States who have been exonerated as a result of post-conviction DNA testing—a fact that may turn one’s notion of the legal system topsy-turvy.
|
Excluding identical twins, each person’s body fluids and tissues contain unique DNA.
DNA extracted from crime-scene samples can be cut into tiny fragments, separated by gel electrophoresis, and then blotted to form a visible pattern, such as a ladder-like series of bands on film or multicolored peaks on a graph.
This characteristic pattern, or fingerprint, can then be compared to that of a suspect. Because of the immense individual variation in DNA, genetic fingerprinting is invaluable to forensic science.
|
Forensic use of DNA analysis in criminal cases began as recently as 1986. Since then, DNA identification, popularly known as “DNA fingerprinting,”(2) has evolved rapidly into the foremost forensic technique for identifying perpetrators, eliminating suspects and clearing people who were wrongly convicted.(1) (See sidebar, “What is DNA fingerprinting?”)
Recent advances in the science of DNA testing have further revolutionized the forensic analysis of blood, hair, saliva, semen, perspiration, fingernail scrapings and other biological tissues left at a crime scene.
Now widely found in life-science labs, the polymerase chain reaction (PCR)(3) method, a molecular copying technique, can generate reliable data from extremely small amounts of DNA. Whereas previous methods required simple sizes as large as a dime-sized drop of blood, PCR testing of nuclear DNA can be done on samples containing as few as 50 to 100 cells (i.e., a visible dot of blood or a single root of hair), even if the sample is old or degraded.
PCR testing of mitochondrial DNA (mtDNA), another recently available fingerprinting method, can be performed even on samples containing extremely old or highly degraded DNA, such as hair shafts and dried bones or teeth.(1)
Scientists interpret DNA test results as an inclusion, exclusion or inconclusive.
An inclusion means that the results obtained from the suspect or other individual are consistent with, or show the same pattern as, the DNA results obtained from a crime-scene sample. In other words, the test yields a “match,” which shows that the individual might be a source of the DNA found in the crime-scene sample. How likely that match is can be expressed using statistics generated from various population groups. If a match is contested, then more in-depth testing can be performed with the remaining evidence and/or DNA.(1)
An exclusion means the DNA fingerprint pattern results yield a “non-match”; thus, the individual is eliminated as a source of the DNA found in the crime-scene sample. Sometimes further testing is needed for the exclusion to be meaningful to the case or to provide evidence for exoneration.(1)
A DNA test is inconclusive when partial or no results indicate that there is too limited an amount of suitable human DNA, or no DNA samples at all, for comparison to crime-scene samples.(1)
For the wrongly convicted who seek exoneration like Charles, the accuracy and widespread acceptance of DNA fingerprinting may not be enough.
Most state and federal jurisdictions have rules restricting post-conviction claims for relief based on new evidence unless an appeal is filed shortly after the conviction. Furthermore, at the time of this writing, only two states, New York and Illinois, expressly permit late appeals based on DNA evidence.
In the absence of an express basis for relief, defense attorneys, such as Barry Scheck and Peter Neufeld, both known for their roles in the O.J. Simpson murder trial, must strategize ways to exploit existing avenues of post-conviction relief to overcome significant procedural hurdles.
With rapidly evolving DNA technology, the role of forensic DNA analysis has profound implications. In a chaotic world that has for years relied on a strong foundation of law, advances in DNA testing have revealed imperfections in the results obtained by the criminal justice system.
But there are many people in the fields of science and law who are tirelessly working to reconcile science and jurisprudence—from Senator Patrick J. Leahy (D-Vt.), who recently introduced a bill that would provide for late challenges to federal convictions, to Scheck and Neufeld, who, through their Innocence Project, take on numerous exoneration cases.
And Attorney General Janet Reno, working closely with The National Commission on the Future of DNA Evidence, takes a strong stand, too. “Using DNA technology fairly and judiciously in post-conviction proceedings,” writes Reno, “will help those of us responsible for the administration of justice do all we can to ensure a fair process and a just result.”(1)
Charles certainly would agree.
1National Commission on the Future of DNA Evidence. Post-conviction DNA Testing: Recommendations for Handling Requests. September 1999.
2Dr. Alec J. Jeffreys, of Leicester University in England, coined the phrase “DNA Fingerprinting.”
3The Polymerase Chain Reaction (PCR) process is covered by U.S. Patents 4,683,202; 4,683,195; and 4,965,188 or their foreign counterparts owned by Roche Molecular Systems, Inc. and F. Hoffman-LaRoche Ltd. No license under these patents to use the PCR process is conveyed expressly or by implication to the purchaser by the purchase of these various products.
