The DNA Fingerprinting Process

dna-fingerprinting-processDNA fingerprinting is a powerful technology that has taken the criminal justice system by storm, providing what has been claimed to be a “tool of stunning precision, able to link the blood, semen, or hair left at the scene of a crime to a suspect’s DNA.” The trial of O.J. Simpson brought the technology world-wide public recognition, but the science of DNA testing is not a new science. The DNA fingerprinting process was developed in 1985 by the British scientist Alec Jeffreys.

At first, DNA fingerprinting was used to establish genetic relationships in paternity and immigration cases. It was first used to secure a conviction of rape in 1987 and is becoming more common in violent crimes, such as assault and battery charges, in which skin, semen or blood is found. Since then, DNA Fingerprinting has been subject to great controversy and scrutiny by the scientific and criminal justice community.

Leading scientists have waged battles in the courtroom over the reliability of forensic DNA fingerprinting. From the accuracy of the testing methods and the quality control standards, to the admissibility and acceptance of DNA testing as evidence in criminal trials, every aspect of DNA testing is being questioned. While the battle wages on in court, it should be acknowledged that the greatest use at this time is exonerating the wrongly convicted. A strong concentration should be placed on the role DNA fingerprinting plays as evidence to exonerate the innocent, while continuing the development of more accurate testing and the acceptance as a conclusive form of evidence at trial is widely gained.

At this stage, the advantages of using DNA fingerprinting to exonerate outweigh the advantages of using the evidence to convict at trial. This paper will outline the various advantages and disadvantages of each, and it will be evident that although DNA fingerprinting is undeniably a true asset to the criminal trial, its greatest use for the moment is for the exoneration of the wrongly convicted.

The technique of DNA fingerprinting relies on the fact that, except for identical twins, everyone’s DNA is unique. The controversy begins when a match is made. Each person’s entire genetic code is unique. However, genetic profiling examines only a tiny fraction of a person’s DNA. Statistical models are used to demonstrate that two DNA samples match.

There are two DNA testing methods currently being used. The most accurate method of DNA profiling, involving restriction fragment length polymorphism, or RFLP, requires extracting genetic material from small amounts of body tissue or fluid – blood, saliva, bone, skin or a hair follicle. This method only requires a bloodstain as small as a quarter. Tiny fragments of the DNA are then used to generate images that look similar to barcodes, which are examined visually for a match with DNA fragments from the suspect. RFLP profiling takes weeks to complete and can cost several thousand dollars per sample. It has been used to link at least 700 individuals to crimes.

The updated DNA fingerprinting process, the Polymerase Chain Reaction (PCR) method, employs an enzyme that scientists can direct towards regions of the DNA that are known to contain variations. The enzyme then copies the region. When the process is repeated about 30 times – with the number doubling each time – more than a billion copies are produced. These can be projected onto a nylon strip in the form of blue dots that delineate the genetic profiles of the segments. Unlike the RFLP method, the PCR system can be carried out in a matter of days. It can be performed on small amounts of DNA, and even on DNA that has begun to degrade.

The major advantage of DNA’s use in exoneration is the conclusiveness of the results. It is simple black and white: if there is no match between DNA found at the scene of a crime and DNA from a suspect, the suspect is automatically absolved. In the case of conviction, there may be no suspect in custody to match with the DNA found at the crime scene.

In 1992 Guy Paul Morin was convicted of killing a 9-year-old Ontario girl. Morin’s conviction was not based on the DNA evidence available because the tests carried out were inconclusive. The sample taken from the girl’s underpants was not pure. The sample had been contaminated by various biological elements surrounding the girl’s body. In 1995, a Boston lab carried out a new round of tests using the DNA fingerprinting process. Scientists removed the other biological material clinging to the underpants to extract an uncontaminated sample of DNA. The evidence was conclusive. The DNA taken from the underpants did not match Morin’s.

Another factor that figures prominently into the positive aspects of DNA fingerprinting is compulsory DNA sampling. An argument in its favor arose from the Morin case. The tests that proved Morin’s innocence also yielded a genetic profile of the unknown suspect. If a national registry of DNA samples was established and the DNA profile gained from the recent Morin test was stored in the national registry, prosecutors might someday be able to bring the real suspect to justice if he were to commit another crime. The practice of obtaining these DNA samples must be closely monitored so as not to infringe upon a person’s constitutional rights. Twenty-six states now keep DNA data on felons as well as thumbprints and fingerprints.

Despite the debates over fairness that DNA testing promotes, many scientists and lawyers insist that the true beauty of “genetic justice” is that it is even-handed. “I’ve been telling people, ‘Stop looking at DNA as the great convicter,’” says Derrill Prevett, a Victoria lawyer who has prosecuted four cases involving DNA evidence. “It’s more objective than that – and it can completely eliminate people from suspicion.”

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