The use of forensics in criminal investigations is, today, a huge element of the process. Furthermore, there has been a surge in the introduction of television programs on the subject, for example CSI. In particular, the introduction of DNA testing has signalled a major breakthrough in the quality of evidence used in court. By examining DNA, it is possible to prove, without reasonable doubt, whether a suspect is innocent or guilty of a crime, just by testing and matching his DNA with that of samples found on the scene of the crime. As with most relatively new discoveries, there are criticisms of DNA. However, if investigators remain mindful of such criticisms, they may serve to actually enhance the credibility of the evidence. Overall, DNA testing has revolutionised the solving of crimes and, if used in conjunction with other forms of evidence, it is likely to develop over the course of the future into even more a reliable form.
The use of DNA testing in forensics has been a breakthrough into solving crimes. DNA examination can reveal the identity of a person who has left just a small trace of themselves at the scene of a crime. DNA can be extracted from very small pieces of the individual, such as a strand of hair or a drop of blood.
Moreover, DNA testing makes for better evidence to use in court. Forensic proof such as DNA is much more reliable as it is based on scientific fact, as opposed to other forms of evidence such as witnesses, which can be unreliable for many reasons.
To successfully identify a person, forensic scientists “scan 13 DNA regions, or loci, that vary from person to person and use the data to create a DNA profile of that individual” (Human). The chances of two people having matching DNA profiles are very low.
DNA samples found at a crime scene can be used to identify suspects. An example of this could be that DNA found in hair, saliva or blood found at the scene could be collected and tested. Following this, suspects can be tested to find a match. Once a match is found, the investigators have proof that the person was at the scene of the crime. In the same way, DNA can be used to prove that the person accused of a crime is actually innocent. Therefore, DNA can be used to either prove that someone is guilty, or prove that they are not guilty (Human).
DNA can be used to identify a victim who has either been so badly damaged in a crime that their body is no longer identifiable, or one who has no friends or family willing to identify the body. Another use of DNA testing within criminal investigations is to prove the family links between different individuals (Human).
In the task of identifying people, DNA can be very successful if exploited properly and thoughtfully. Sections of the DNA sequence which are most variable in humans should be used. In addition to this, these sections should be big enough to compensate for the point that reproducing among humans is not completely haphazard. Furthermore, DNA testing should be used in conjunction with other types of forensics.
For example, if in a crime scene, O blood type is discovered, more tests need to be done as up to forty-five per cent of American individuals have type O blood. If however, some hair of the suspect is also found on the scene, and the hair is blond, the investigators have progressed slightly further. However, having type O blood and having blond hair as well, are common. If, additionally, there are footprints at the crime scene that have been made with Nike Air trainers, the investigators then have another element to cross match with the suspect and, therefore, the investigation is more likely to be solved (Human).
In isolation, neither the blood type, the hair colour or the footprints are particularly strong pieces of evidence. However, by relating and interlinking the different pieces of evidence in this fashion, it is more probably that the suspect can be proven to be the wanted person. In this way, by accumulating bits of linking evidence in a chain, where each bit by itself isn’t very strong but the set of all of them together is very strong, you can argue that your suspect really is the right person.
Of course, if some blood or hair is discovered at the scene then Forensic scientists will be able to test the DNA, and have almost complete proof about whether the suspect is a match.
The same theory is applied to DNA. Matches can be found by identifying and comparing two or three different strands of DNA found at a scene to those of a suspect. However, even if positive, these two or three matches are not enough to be certain that the suspect is the correct person. However, if all thirteen sites of DNA are tested, and matched successfully, the investigators can be extremely confident that they have the right person (Human).
DNA samples are usually acquired from collecting bodily fluids or pieces of skin present at the crime scene or on or around the dead body. Such samples can also be gathered from victims who have been sexually assaulted in a serious manner. A victims fingernails often contains skin from the suspect, and so these skin sleeks are scraped and tested as part of the investigation (Taking).
DNA does not have to be found in a suspicious part of the crime scene. It can be found, for example, on tea cups, cutlery and other similar items. Once a skin or fluid sample has been gathered, the DNA will be retrieved using a “solution of salt or chloroform and phenol” (Taking). It can heated, split and then analysed by the forensic scientists.
When the double helix has separated into two sections; and after the DNA has cooled down from the process, the two halves will self-repair. “Each cell contains around six feet of DNA strand when viewed under an electron microscope” (Taking). It takes scientists a long while to thoroughly examine DNA samples.
In order to understand the gravity of the introduction of DNA testing in crime investigations, it is important to consider its history.
More than a century ago, fingerprinting was identified as the most reliable and accurate method of ascertaining a suspects presence at the crime scene. When introduced, the this technique was ground-breaking, and led to many arrests and convictions. Much more recently, however, DNA has become even more ground-breaking and, indeed reliable (Forensic).
DNA typing was originally defined in 1985, by a scientist called Alec Jeffreys. Dr. Jeffreys discovered that “certain regions of DNA contained DNA sequences that were repeated over and over again next to each other. He also discovered that the number of repeated sections present in a sample could differ from individual to individual. By developing a technique to examine the length variation of these DNA repeat sequences, Dr. Jeffreys created the ability to perform human identity tests” (History).
The technique of extracting, testing and matching DNA samples was originally put to use late in the 1980s, to condemn a male suspect of raping, and making pregnant, his thirteen year old daughter. Investigators obtained tissue samples from both the man and the aborted foetus. The DNA was analysed and compared, and matched. This evidence proved the man’s crimes, beyond reasonable doubt, and the man ended up confessing (Forensic).
Since then, the use of DNA in court has been popular. It was, for example, used as evidence in the famous trial of OJ Simpson, in 1995. When this trial originally went to court, it seemed to most who were involved that Simpson was going to be convicted and prosecuted with the murder of his wife and her friend. However, when the defence was presented, it was revealed that there was reasonable doubt about the DNA evidence, in that the blood samples had been mishandled. Therefore, rightly or wrongly, Simpson was acquitted. At this time, the use of DNA testing as criminal evidence was relatively new, and therefore mistakes were still prone to happening, especially when it came to protocol such as handling the samples correctly and guaranteeing now cross-contamination or infection could occur.
Furthermore, DNA evidence was used to prove the innocence of the late Sam Sheppard. Sheppard was a well-known doctor who was “accused of killing his wife in 1954, but claimed a “bushy-haired” man did it” (Forensic). DNA examinations proved that the blood found at the crime scene was neither that of the doctor, nor his wife, proving that another person was present. There are countless other stories just like this one, and since the introduction of DNA testing many people have been found innocent and consequently released from prison (Forensic).
When using DNA evidence, protecting the crime scene is vital. If a crime is to be solved successfully then evidence must be protected and preserved. Furthermore, when DNA samples are collected, the investigators must do so wearing appropriate gloves, and place the samples into sterile receptacles, in order to avoid any chance, or accusation, of contamination or mishandling.
It is crucial that all workers at the crime scene avoid “smoking, eating, drinking, littering or any other actions which could compromise the crime scene” (Transportation). DNA evidence is much more vulnerable than other kinds, and therefore all persons involved in the investigation must be mindful of contamination at all times. Additionally, DNA should be kept away from direct sunlight and should not be placed in a hot room or car. DNA evidence is most successfully and reliably kept in a cold area.
Perhaps one of the most amazing aspects of DNA evidence is that it can be used and analysed for years after the original incident. According to a DNA Initiative website, “Nuclear DNA from blood and semen stains more than 20 years old has been analysed successfully using polymerase chain reaction (PCR). Samples that have been stored wet for an extended period of time should be considered for testing only using PCR and may be unsuitable for DNA analysis. Mitochondrial DNA analysis has been performed on very old bones, teeth, and hair samples” (Transportation).
Despite the fact that DNA is so ground-breaking and has helped to convict and sentence many dangerous criminals, it has still experienced criticisms over its time. It appears that, predictably, many defence lawyers choose to slate it when given the opportunity, though this is arguably because it harms their defence in court. Some people contest that DNA analysis does not account for ethnic diversity, and it is true that little is known about the sequencing of DNA across people of differing races. Some also claim that evidence can be mishandled by the police, as was demonstrated in the OJ Simpson trial. If samples are not handled very carefully, they can become damage and cause the DNA analysis to be unreliable. While this is a viable concern, the use of DNA in this way is without doubt the most reliable and effective forensic evidence in existence (Objections).
Interestingly, as OJ Simpson was acquitted based on concerns over the handling of DNA evidence, it could be questioned as to what the outcome would have been had there been no DNA involved. It is possible that if the trial had happened ten years earlier, the police and prosecution may have relied more heavily on other forms of evidence as, obviously, DNA testing was not an option at this time. If the police had focussed on different forms of evidence then perhaps OJ Simpson would have been found guilty and sentenced for the crime.
Overall, it seems that DNA testing has enhanced the criminal justice system, in that many people have been proven both guilty and innocent, where as they may not have been without the existence such techniques. However, it is also possible that errors and concerns with the DNA evidence has also caused guilty people to be acquitted and released.
The introduction of DNA analysis has revolutionised the process of criminal investigation, and has certainly proved a great deal that may not have been proven otherwise. However, it seems important to remember that DNA is just one form of evidence and, if it is to be at its most useful, it should be combined and linked to other types of evidence. Moreover, the different types of evidence should all be given importance, while being mindful that certain types are more reliable than others. DNA has a great advantage over other forms of evidence in that it is based on science, and therefore its results can be considered as fact, unless, of course, the evidence has been contaminated, damaged or mishandled in some way. A suitable comparison is that of witness evidence and DNA evidence. Witness statements can be extremely valuable, as a person who saw or heard something of the crime can provide an insight which the investigating officers would otherwise be unaware of. However, humans are prone to misremembering, and sometimes exaggerating, whether consciously or subconsciously. As DNA is based on scientific analysis, there is no room for unreliably memories or for exaggerations.
However, DNA cannot be asked further questions about what happened at the crime. Although DNA may prove, beyond reasonable doubt, that a man killed his wife, it cannot explain the circumstances behind it. Factors such as whether the man acted in self-defence, or whether he was provoked, or whether it was an accident, cannot be explained by a DNA sample. Therefore, it is imperative that all other available sources of evidence are taken into account, and used in conjunction with the evidence produced by DNA testing.
Overall, DNA testing has provided a wonderful breakthrough, both in science and in crime. As scientists learn more about the techniques, it is likely that this type of evidence will become ever more useful, in many different contexts. As with any new phenomenon, DNA has its critics. However, these critics often have a vested interest in discrediting such a reliable form of evidence, for example defence attorneys. As more developments take place, the future of solving crime looks bright.
Forensic DNA. Oracle. Retrieved from http://library.thinkquest.org/28599/courtroom.htm
History of Forensic DNA Analysis. DNA Initiative. Retrieved from
Human Genome Project Information. Oak Ridge International Laboratory. Retrieved from
Objections to DNA Testing. Oracle. Retrieved from
Taking DNA Samples. Explore Forensics. Retrieved from
Transportation and Storage. DNA Initiative. Retrieved from