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The Reliability Of DNA Testing


Sumber: http://www.numerex.com/inside-our-DNA/applications

The public in Malaysia has already learnt the use of DNA (deoxyribonucleic acid) in criminal cases, particularly rape and sodomy. The information of the DNA application was reported vastly in the media.

Undoubtedly, people have been provided with sufficient information to understand the role of DNA in the investigations. In fact, the public has made an assumption that DNA evidence is everything in crime fighting.


Down the marvel of the Almighty. Source: http://rec-dna-app.weebly.com/

Looking back on the history of the use of DNA in solving crimes, it was pioneered in Britain when a British genetic scientist has produced a DNA fingerprinting technique which in turn revealed the DNA profiling in 1985. Professor Sir Alec John Jeffreys (Wellcome Trust) has studied deeply and implement these techniques to help with the police investigation.

He has introduced the application of a DNA profiling in a police investigation since. Until now, the DNA technique has been extended to a variety of application in forensic science purposes.

In general, the purpose of the use of DNA is to identify an individual from biological samples from; either at the crime scene, an assault victim, or from the accused.

The applications of DNA are as follows (Butler, 2008):

To test the probability of an accused to be the criminal


Example of DNA application in forensics. Source: http://www.mhhe.com

The basic principle in forensic was introduced by Edmund Locard with his theory; “every contact leaves a trace” (Petherick, 2010). It gives a great impact to the field of forensic investigation. Based on this theory, every crime scene will be cordoned by the police to preserve the scene and its evidence.

During the investigation, the forensic unit will collect the physical and biological evidence found for analysis at the forensic laboratory. All biological samples such as blood stains, hair and others are collected and stored safely before transported to the laboratory.

After the DNA testing performed in the laboratory, they will obtain the DNA profile for the collected samples. To continue with the investigation, a set of DNA profile is needed from the accused for comparison.

If the DNA profile of the accused is similar with the crime scene DNA’s profile, the probability to link the accused with the scene of crime is high.

Paternity and Maternity Testing

Nowadays, it is quite often for the media to report about the events of abandoned babies. Babies whom born out of wedlock are often being discarded like trash. If the baby is lucky, it will be saved by the passers-by. But most of the time, the baby was left to die and at times attacked by animals.

To seek for these cruel parents, a DNA testing needs to be conducted. First a DNA sample has to be collected from the unfortunate baby for a profile. It will then be compared with the DNA profile of the accused mother and the suspected father.


Petikan akhbar tentang pembuangan bayi.
Sumber: http://www.teratakarmo.com/2010/04/kes-buang-bayi-berleluasa.html

The principle is easy. The individual sets of chromosomes are inherited from the mother and the father. If the baby’s DNA profile match with the profile derived from the accused mother and the suspected father, then there is a high possibility that the baby was their child. Further investigations will be carried out by the police to get the confessions from the accused. Other type of evidence that could support the case is also required.

Investigation on Bones and Human Remains

Similar to the other cases, a set of DNA profile from the collected bones found at the scene need to be obtained as a reference. The problem that may arise is the absence of the profile to be compared with.

In this situation, if the bones were believed to belong to the specific victim, the victim’s DNA samples may be obtained from his personal belonging. DNA can be extracted from his tooth brush, or a strand of hair from his home.

 

Two sets of DNA profiles from personal belongings and bone.
Source: http://maxwellinstitute.byu.edu/files/Forensic-DNA-Testing.pdf

Identification of Victim of Mass Disaster

In every situation, DNA profiles are needed from the victims of mass disaster. The principle is quite similar to the above case; which is to identify the victims. However, there is another issue that may arise in such situation.

Normally for cases involving a disaster, there are difficulties in bringing out the dead bodies of the catastrophic incident. It takes time due to various factors such as the safety of the team, suitability of the location, the equipment used other concerning factors etc.

Hence, the victim bodies and remains had already decomposed at the time they were brought out. How can the remains be identified? If the bodies are intact, the identification process is easier. But if the remains are mixed with other victims sometimes it is difficult to tell whether the collected remains come from a single person or more. This situation could cause problems.

One of the questions to be answered is that; whether this piece of bone or limb belongs to a man or a woman? Thus, through DNA identification techniques, it helps the investigators to identify the victims in any condition, provided the comparison data is available.

  One sample showed the victim of a man while another is a woman based on chromosome X and Y.
Sumber: http://maxwellinstitute.byu.edu/files/Forensic-DNA-Testing.pdf

Conclusion

The purpose of the forensic DNA is to give the identity of any person involved in an incident. However, it is possible in the future, that DNA may plays a more important role that exceeded our expectations.

References

  1. Butler, J. M. (2008, 08 21). Forensic DNA Testing: How Are Crimes Solved with DNA Analysis? Retrieved 07 08, 2013, from http://maxwellinstitute.byu.edu/: http://maxwellinstitute.byu.edu/files/Forensic-DNA-Testing.pdf
  2. Petherick. (2010). Forensic Science Central. Retrieved 07 08, 2013, from http://forensicsciencecentral.co.uk/edmondlocard.shtml
  3. Wellcome Trust. (n.d.). The Human Genome. Retrieved 07 08, 2013, from http://genome.wellcome.ac.uk/: http://genome.wellcome.ac.uk/doc_wtd020877.html

 

Last Reviewed : 17 October 2013
Writer / Translator : Khairul Adli b. Nikman
Accreditor : Dr. Shahidan bt. Md Noor