DNA Identification

Some people think that DNA identification requires the analysis of the all of the DNA found in a sample that comes from a crime scene. That would be a formidable task. Any person’s DNA has at least 3 billion different letters. The process of DNA identification does not look at all of those letters. It looks at only 10% of them, those that molecular biologists have found to exhibit tell-tale differences from one human to the next. An analysis of that small 10% gives legal experts all of the information they need to know. If that amazes you, then read more below.In 1992, law enforcement officials made no secret of the anniversary that they wanted to acknowledge. That was the anniversary of the first occasion when fingerprints were used to identify the perpetrator of a crime. Not long after that, the public heard a great deal about a new way to identify a criminal—DNA identification.
Many members of the public gleaned some information on DNA identification from broadcasts of the trial of O.J. Simpson. Specialists on both sides presented the jury with information from a DNA analysis of materials from the crime scene. They faced a real challenge, because no member of that jury had taken a biology course that had included extensive information on DNA identification.
The O.J. Simpson trial highlighted the importance of DNA identification. The analysis of the DNA from blood and bodily fluids obtained at a crime scene can help to “fill in the blanks.” It can help add information that was missing, due to a lack of sufficient fingerprints.
In order to fully appreciate the value of DNA identification, one needs to learn the facts that relate to the science of molecular biology: 1) any human criminal shares with other humans 90% of the 3 billion letters in his or her DNA;  2) 10% of each individual’s DNA has a “spelling” that differs from the “spelling” of another individual; 3) humans can, over time, exhibit at any one of at least 3 million spelling differences.
That fact makes the DNA of each individual unique .That fact underscores the ability of DNA identification to point a finger at a guilty individual. That fact illustrates why DNA is of interest to government security experts.
Yet those same experts understand that they can not have people at the airport collecting blood samples from the waiting passengers. They also realize that retina scanning could serve as an equally effective way to identify suspected terrorists. Unfortunately, the public is not ready for the laser scanning that goes with an analysis of the retina. That is why the combination of retina scanning and DNA identification does not loom on the horizon for the near future.
Meanwhile, legal experts continue to seize on the information that comes from the molecular analysis of DNA. Legal experts gather evidence at a crime scene and pass it to a lab equipped with a PCR machine. That machine can magnify any small sites of variation in the DNA from blood or other fluid. An examination of such sites of variation will then disclose any markers of difference.
If a marker of difference found in the evidence matches a marker of difference found in the DNA of a suspected criminal, then the case against that criminal becomes much stronger. By the same token, a missing marker difference diminishes the strength of the case against the alleged criminal.