paternity test

Smudges Don't Matter With DNA Fingerprinting

It sure is elementary, dear Watson … look what science has come up with now!

Sherlock Holmes' eternal frustration would be in finding a fingerprint on a doorknob, only to realize it was smudged beyond use. Imagine his delight if he had lived in our times, to know that a single hair, skin fragment or drop of saliva could incriminate a person, even if the culprit had been wearing gloves at the crime scene!

DNA fingerprinting has been around since 1985 and was invented by Sir Alec Jeffreys, one of the world's most respected and renowned genetic scientists. It can be used in medical, social and criminal applications. Medical professionals use it to establish whether twins are identical or fraternal, which is vital information in cases of organ transplantation, and even to determine whether bone marrow grafts have taken or not. It's also used for forensic identification and paternity testing.

Ghanaian boy proven as son
The first instance to which DNA fingerprinting was applied was the case of a Ghanaian woman whose family had become UK citizens. One of her children, a teenage son was refused re-entry to Britain after a trip to Africa, when immigration authorities believed the boy to be suspect. They insisted that he wasn't a member of the family, and that he was being smuggled in as a substitute. Ordinary blood group analysis was not conclusive enough to resolve the case. DNA fingerprinting came to the rescue and proved that the boy did indeed belong to the family, as the evidence presented was overwhelming.

Scene of the crime comes to life
It was originally thought that a particular young man with a record of minor sex offences had perpetrated the UK's Enderby murders. The man confessed to one murder but denied any knowledge of the other. Sir Alec himself was asked to use DNA fingerprinting to examine the forensic evidence in detail in both cases. The results proved the man's confession and had him acquitted on the second charge. An investigation ensued using the semen samples found at the scene, and the world's first DNA manhunt brought to justice the real murderer of the other victim.

Personal identification
The US Army employs DNA fingerprinting as a means of cataloguing and accounting for all enlisted personnel. This is particularly useful in the event of death where the body has been damaged beyond recognition. Similarly, DNA fingerprinting was used to establish the identities of many of the victims of the World Trade Center attacks in 2001. Over twenty thousand fragments of tissue were collected and used to extract DNA.

Fast facts

  • DNA materials must be extracted at a temperature range of 50°-60° Celsius. Temperatures exceeding 60° C may denature the DNA.
  • With the exception of identical twins, no two people on earth have the same DNA.
  • Since the late 1980's, scores of inmates have gained their freedom based on new evidence developed using DNA fingerprinting techniques. One such case is that of the bashing death of Mrs Marilyn Sheppard, whose husband, Dr Sam Sheppard, was jailed for ten years for her murder. Forty-five years after his conviction, his son requested DNA fingerprinting to disprove his father's guilt once and for all. The chronology of the case is well known to forensics fans on the Internet.
  • Only a handful of laboratories around the world possess the advanced technology required to conduct DNA fingerprinting.

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