DNA Testing For Forensic Evidence

DNA or De-oxy Ribonucleic acid can be looked at as an integral part of the human body or as an interesting piece of evidence. The beautiful color of your eyes, the shining hair color, bone density and much more is due to the DNA. Each cell in our body consists of a DNA strand and some of the DNA formations are in a particular code like AATTGCCTTTTAAAAA. These are called coding DNA’s and this same code is passed over from the parents to the offspring through sperm and egg. This is also the type of DNA that forensic experts use for various testing purposes.

In the last decade or so, forensic science has advanced at a faster rate and DNA is used not only for finding criminals but also solving cases, which have been long buried in a heap of files. DNA testing for forensic evidence can lead to the following:

1. It can assist in solving crimes like murders, rape etc. 2. It can assist in archeological discoveries like determining the origin, history and physical or health conditions of the mummies of Egypt 3. Testing DNA can also determine the family history 4. DNA testing can provide information regarding the parents, the mother or father of a child.

There are millions of possibilities and results that can be arrived through DNA testing but the truth is that forensic experts and scientists have only been able to uncover a small but significant part of the mystery of DNA. DNA testing for forensic evidence can be broadly termed in two main groups. The first type is called the RFLP testing and second is PCR based testing. The RFLP DNA testing process can only be done when a large amount of DNA is available. The DNA evidence normally derived from the crime-scene is normally present in smaller amounts and can also be too old, which makes it unsuitable for RFLP testing. When conditions are warm or moist then it may cause the DNA degradation, which will again make RFLP DNA testing almost impossible.

One the other hand, PCR-based forensic testing will require less DNA as compared to RFLP testing. Even if the DNA is in a partially degraded condition, PCR testing DNA is possible. Most forensic experts have to keep in mind that even DNA samples for PCR testing has limitations as far as DNA degradation and sample size is concerned.

One aspect that the PCR-based test is extremely sensitive to is contamination of DNA found at the crime scene. Contaminations can even happen in the test laboratory. Basically, contaminants in DNA can influence the PCR results and lead to the failure of the test. The RFLP tests are preferred as compared to PCR because the latter is prone to error.

DNA testing using the RFLP method requires forensic experts to cut the DNA using a restriction enzyme before they can use it to find information. This restriction enzyme is important because it can recognize a particular sequence of the DNA like the AATT sequence. The commonly used restriction enzyme is Hae III and the choice of enzyme depends purely on the forensic experts.