What is DNA fingerprinting, and what are its uses in police work?
DNA, i.e., Deoxyribo Nucleic Acid, is the fundamental genetic material in every living being that passes on the trait or character of parents to their children. Every living cell of the body contain DNA which is similar for a particular body, i.e., person's DNA is the same throughout the body may it be in the blood, in skin, bone, the root of the hair, semen, vaginal or rectal cell or any cell from other parts of the body as well as bone marrow but not red cells in blood as they are devoid of the nucleus.
DNA has a double-helical structure like a twisted ladder. The basic components of DNA are sugar-phosphate and nitrogenous bases (adenine, thymine, guanine, and cytosine).
The supports for the steps of the ladder are made of an alternate unit of sugar and phosphate, and the step themselves are made of nitrogenous bases, which occur in specific pair. Adenine always pairs with thymine and cytosine combines with guanine.
The order of these nitrogenous base pairs is different from person to person. There are millions of base pairs in a person, and each person has definite and different sequences. Every person can be identified solely by the sequences of these base pairs. Scientists are able to determine whether two DNA samples are from the same person, related person, or non-related people.
The value of DNA Evidence
In recent years DNA profiling has emerged as a powerful investigative tool. With the exception of identical twins, no two persons have the same DNA. DNA profiling can be used in the following cases:-
1. For Identification purposes in cases involving rapes, murders, etc.
In cases in which biological matter is involved and found on the scene of the crime, may it be of the victim or the criminal, it is helpful in identifying and connecting the victim and the criminal with the scene of the crime.2
2. Paternity and maternity disputes
The intermingling of DNA of parents determines the DNA of the next progeny i.e., DNA of a child shows the characteristics of the DNA of mother and father. As DNA is different for different people, the combination formed by two unique types is also unique.
3. Cases of switched babies
Sometimes, due to sheer negligence or otherwise, newborn babies got changed, or there is more than one claim of a young child. Then, with the help of DNA profiling, the child can be restored to his/her legitimate family members.
4. Pedigree analysis for establishing links with a family.
5. Cases involving adultery charges against husband/wife.
DNA fingerprinting can help in cases where the matter of illicit sexual relationship is in question.
6. Identifying the legal heirs.
DNA fingerprinting can establish whether a person is genetically attached to a person or his family.
Source of DNA
1. Blood
2. Semen
3. Bones
4. Tissues
5. Hairs
6. Various secretions of the body like saliva, urine, tears, sweat, etc.
DNA is important evidence, but an investigating officer or the first officer on the scene of crime must be very careful in handling DNA evidence. It is because the elements of contamination potential are very high as everyone has DNA, and anybody could be a source of contamination, including the IO himself.
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