Dna Testing for Forensic Purposes

One of the significant developments in Forensic science has been the use of DNA Testing. This method of testing has helped solve many crimes that would not have been possible a few decades ago. More importantly it has been able to solve the crimes with a very high degree of accuracy resulting in avoidance of other circumspect or doubtful methods of investigation.

Every human being on the earth has genes. These genes are a unit of heredity and are also unique for each person. They are made up of made up of a number of molecules of DNA (Deoxyribonucleic Acid) in a particular sequence that is unique for each person. Thus a person’s genes can be identified and mapped. This system is known as DNA profiling.

In Forensic science the DNA from biological samples such as human hair, blood, semen, skin or saliva found at the scene of the crime is compared with the DNA of the suspect person and by the comparison it can be found whether the suspect person is innocent or guilty. This process is called genetic fingerprinting or DNA profiling. The system of DNA profiling is normally accurate only if the samples at the scene of the crime are not contaminated although as technology develops the capabilities of extracting DNA have improved immensely.

The first person to be sentenced to life imprisonment in the United Kingdom on the basis of evidence of DNA profiling was a rapist and murderer by the name of Colin Pitchfork. In the years 1983 and 1986, bodies of two young teenage girls were found. These girls had been raped and strangulated in a small town of Narborough, when each of the girls was returning home alone late in the day. There were no witnesses of the crimes, but the DNA profiles of the samples drawn from the scene of the two murders confirmed that the crime was perpetrated by the same person. Investigations led to the arrest of Richard Buckland, a young lad who confessed to murdering the second girl and denied that he had anything to do with the murder of the first girl. The DNA profile of Richard Buckland did not match with the DNA of the samples drawn at the scene of two murders. Further investigation led to the arrest of Colin Pitchfork in September 1987. The DNA profile of Colin’s blood sample matched with the DNA profile of the killer of the two girls. Colin Pitchfork confessed and was sentenced to life imprisonment in 1988 and became the first person to be convicted based on the evidence obtained from DNA profiling. Richard Buckland was the first person to be proved innocent of the crimes alleged to him by DNA profiling.

DNA testing can be done on samples of different material obtained from the scene of the crime. The non standard samples can be blood stains from clothes, tissues and tampons, clothes such as caps, bandanas, underwear, cigarette butts, gum, hair (at least four to five hair strands with hair roots), post mortem tissues. Standard samples are obtained from Buccal swabs (swabs of saliva taken from the cheek inside the mouth), blood, semen or sperm, or dry umbilical cord. The success rates vary depending on the samples and the condition they are in. The methods of preserving the samples also vary from preserving in dry ice to tubes to simple paper envelopes.
The National DNA Index (NDIS) has thousands of records of DNA profiles of samples drawn at the scene of the crime and as well as DNA profiles of body fluid samples furnished by known offenders. This data has been used to match and solve crimes and has resulted in over seventy thousand convictions. The NDIS and the DNAAU-II departments have helped in tracing missing persons and also in identifying unidentified bodies.

Forensic investigations based on DNA profiling have come a long way since the first studies were done during the 1980s. Paternity tests can confirm that the alleged father is not a father with one hundred percent accuracy and can conclude that the alleged father is the father with 99%+ accuracy. The results are accurate even when the mother is not tested. Infidelity or ancestry can also be tracked based on DNA profiles.

A lot of innocent victims have found freedom after DNA profiling proved that they were no way connected with the crime. As the testing methodologies are further refined, DNA Forensic testing will continue to cement itself as a very important tool in crime investigation.