Majority of the regions between genes are just non-functional. Such regions, which constitute about 99% of the total DNA, show tremendous variation from person to person and help in identification of the individual by what is now popularly called DNA Fingerprinting. DNA fingerprinting is useful for establishing paternity and maternity in criminal cases. Blood or semen stains, hair, or items of clothing found at the site of crime provide biological evidence through DNA fingerprinting. Hence, DNA fingerprinting is important in forensic research to gather evidence about criminals.
The genetic print-the DNA of a person/her genetic profile, has 2 great advantages: it's unique for every person, and it's almost impossible for a human beeing not to leave any trace when he commits a murder.
In perfect conditions, the forensics biochimists only need 100-150 nanograms of "biologic material"(blood, residual skin and secretions) to make the connection between the genetic profile of an individual and the traces that were left at the scene of a crime.(no more than a microscopic layer of cells that a person leaves if he touches with a finger a box of matches) :)
Forensics uses DNA to help solve cases because DNA is unique to each individual. This can help to find anyone who may have been involved/committed a crime. DNA is typically use to help identify a victim and the suspect that committed the crime.
Some examples where DNA correlates to solving a forensic case:
- A woman is murdered and cannot be identified through visual means. They sample her blood to confirm who she is. Then they search for any other DNA such as hair, skin cells, blood, or in the event of sexual assault, semen to see who the suspect is.
- Someone was robbing a store and accidentally cut themselves along the way or some of their hair was left behind. The DNA can be ran through the DNA database and if someone is already in it, they just found out the identity of the thief.
- Someone is attacked and fights back by scratching the assaulter. The skin under their fingernails can be used for DNA analysis to find out who the attacker was.
- A victim is raped and there are traces of semen. The semen can be analyzed for identification.
These are some of the many examples of DNA being used in solving forensic cases.