The characteristics of all living organisms, including humans, are essentially determined by information contained within DNA that they inherit from their parents. Living organisms that look different or have different characteristics also have different DNA sequences. The more complex the organisms, the more varied is their DNA sequences. DNA fingerprinting is a very quick way to compare the DNA sequences of any two living organisms.
Like nearly everything else in the scientific world, nothing about DNA fingerprinting is 100% guaranteed. The term DNA fingerprint is, in one sense, a misnomer: it implies that, like a fingerprint, the VNTR pattern for a given person is completely unique to that person, although it actually isn't. In fact, a VNTR pattern can just present a probability about whether the person in question is really the one to whom the VNTR pattern (of the criminal evidence, etc.) belongs, or not. The probability might be 1 in 4 billion, which would indicate that the person could be matched with the DNA fingerprint.
The probability of a DNA fingerprint belonging to a specific person needs to be reasonably high--especially in criminal cases, where the connection helps establish a suspect's guilt or innocence. Most people will agree that an innocent person should not be sent to jail while a guilty person is allowed to walk free. In fact, the number of convicted prisoners found to be innocent after a DNA analysis of evidence has caused some US states to reconsider previous cases. Now, they are going back and taking another look at some cases where DNA evidence still exists.
Like the fingerprints that came into use by detectives and police labs during the 1930s, each person has a DNA fingerprint. Unlike a conventional fingerprint that occurs only on the fingertips and can be altered by surgery, a DNA fingerprint is the same for every cell, tissue, and organ of a person. It cannot be altered by any known treatment. It is now possible to test tiny pieces of biological matter such as a hair and get a DNA fingerprint. It has also become possible to get a DNA profile from matter which has decayed, or is not fresh. In addition, the tests have become much faster and matching easier because there are more and more data banks. Consequently, DNA fingerprinting is rapidly becoming the primary method for identifying and distinguishing among individual human beings.
The use of DNA fingerprinting in law is only 15 years old. In the US, 45 states now collect DNA from those who have been sentenced for sex offenses. Other states collect samples from those convicted of other crimes, usually violent ones. Recently, there has been pressure for an amendment in criminal law to have burglary added to the list of crimes that make an offender subject to collection of DNA information. This move was inspired by an analysis of crime statistics from Florida, which indicated that about 52% of people found guilty of burglary will eventually be found guilty of a murder or a sexual offense.
There is a national database of DNA fingerprints for offenders, to which 20 states are already linked. It allows the police to match evidence from the site of a crime with the DNA fingerprints available, even when no local suspect has yet been identified. As David Coffman, an expert at the DNA database, noted: "The investigators used to phone me with names. Now, I phone them with possible matches for the cases they are investigating."
The use of DNA evidence will probably give rise to objections from people who will claim that it is an invasion of privacy. In the coming years, it is going to be interesting to follow these debates and the advances in DNA technology.