The average viewer of crime dramas on television or film, as well as the interested fiction and non-fiction reader, will undoubtedly be aware of the benefits of using DNA testing as part of a criminal investigation. While witnesses can lack credibility or fail to recall relevant details, and other circumstantial evidence may be inconclusive, DNA has the potential of identifying the actual perpetrator of a crime with an astonishing level of accuracy. This makes DNA testing not only good for crime, it makes it necessary.
DNA testing, in many ways, has its origins in the 1920s, with the advent of blood-type testing. While blood type is general in nature, testing individuals and comparing it with samples of blood found at the crime scene could help to eliminate certain suspects. This began the trend of using bodily material as a way to identify individuals involved in crimes, an approach that is mirrored to today with DNA testing.
The first reliable DNA test used to identify individuals became available in 1985 through the research of Sir Alec Jeffreys. Subsequently, it became increasingly used as a tool to identify suspects in criminal cases, beginning with agencies such as the FBI for high profile cases, and eventually moving down to the state and local level for all manner of criminal investigations.
Further advancements in testing have allowed for more discriminating tests, and ones which allow for the use of very minute or degraded samples, thus allowing scientists to increase the accuracy of identification. In the early days of DNA testing, the samples obtained from hair, saliva, semen, blood and other identifiers needed to be quite fresh in order to match the sample to a specific person. Due to these early problems, DNA was seen as unreliable for use in court as evidence. As better techniques were developed and the science of genetics in general improved, the tests became more reliable and were gradually accepted into the court system. The first case where DNA was admitted into evidence was Andrews v. Florida in 1988.
Identification of Suspects
Obviously, the greatest benefit that comes from DNA testing is the ability to identify who exactly was present at the time of a crime. While characterized as circumstantial evidence (meaning it does not directly prove innocence or guilt), it nonetheless serves as a very powerful tool for both an effective prosecution and defense. To illustrate, let us say that following a rape, the police find witnesses that attest to having seen a particular individual following the victim around the time of the incident. Without any other evidence, this may be insufficient to mount an effective prosecution, especially if for whatever reason the victim can't identity the suspect. With DNA testing, though, one can take whatever samples are available and compare them with that of the suspect. If there is a match, then the case has a much better chance of being successful. If it is not a match, then the suspect can use that to defend against any charges filed. We can thus say that DNA testing is a double-edged sword, useful both to defense attorneys and the state in its efforts to secure convictions.
In recent years, much attention has been focused on how DNA testing can exonerate those who have already been convicted of a crime though other evidence. According to Reason Magazine, as of 2008, around 220 people have been exonerated of crimes they did not commit. This includes people who have been in prison for years on charges of murder, rape and other serious violent crimes. Even death row inmates on the brink of execution have been saved at the last minute due to DNA testing of samples that had been sitting in storage for several years. Despite Blackstone's famous line that it is "better that 10 guilty persons escape than that one innocent suffer," our current system sometimes seems to lean on the side of zealous prosecution and high conviction rates, often resulting in innocent people going to jail through misuse of evidence. Some studies have shown that forensic scientists, who are supposed to maintain an impartial attitude when analyzing evidence, have been found to be actively skewing evidence in favor of the prosecution and at the expense of a suspect, according to data collected and analyzed in the book "Forensic Science Under Siege," by Kelly Pyrek. In light of this disturbing reality, impartial DNA testing can help to correct this problem by providing suspects a way to defend themselves when the whole system seems to be against them.
While there are many good uses of DNA testing for crimes, there is also the potential for abuse or negligence. For example, if there is more than one DNA sample at a crime scene, it can be difficult to determine what, if any, relationship a person has to a crime. If there are other samples around from other sources, then the situation becomes very complex and DNA testing can become inconclusive in determining guilt or innocence.
Also, there have been cases where DNA tests have been tainted through contact with other samples, and where the results of tests were misstated or mis-characterized in court. It is clear then that DNA testing is merely one more tool available to enhance the pursuit of justice and by no means the Sine qua non of criminal investigation.
There is a growing call to establish a national DNA database to augment the one currently maintained by the FBI on convicted criminals. Some call on everyone, regardless of their criminal history, to be included. Others, seeking a less controversial approach, seek to obtain DNA samples from anyone arrested or questioned in relation to a crime. These measures bring up important concerns for privacy and the presumption of innocence enshrined within our legal institutions. Investigations into high profile crimes, for example, have already been used to ask otherwise innocent people to "volunteer" their DNA in order to be eliminated as a potential suspect. This entails citizens having to prove their innocence as opposed to the state having to prove guilt beyond a reasonable doubt. Therefore, like all technological advancements, DNA testing has the potential for negatively altering our society in ways that outweigh the benefits that it provides.