DNA - a talented detective

Colin Pitchfork - a 27-year-old baker in England - occupies a special position in the annals of police because he was accused by his own cells. This man raped and killed two female students. Crime is detected by DNA testing.

Alec Jeffreys geneticist (Photo: le.ac.uk)

In 1984, at Leicester University (England), geneticist Alec Jeffreys invented DNA identification techniques. At that time, British police were investigating the case of two rape girls killed and killed. Police took blood from more than 5,000 men aged 13-30 in three villages around the place where the murder occurred. After analyzing and contrasting, the police found that the DNA of the baker Colin Pitchfork was the same as the DNA sample in the semen collected from the victim's body.

Sentenced to life imprisonment, Pitchfork became the first criminal to be arrested for DNA testing. Since then, DNA test results have been accepted as evidence in court in many countries around the world and have been helpful for law enforcement agencies.

In contrast to Pitchfork is the case of Rodney Buckland. DNA saved this 17-year-old man. At first, Buckland was arrested for being suspected of being involved in a murder. But then he became the first person in history to be vindicated by DNA.

So far, thousands of criminals have been arrested and sentenced by DNA identification techniques. There have also been many people who were unjustly assisted by DNA, many of whom have been behind bars for many years, some even about to be put on the scaffold.

Also thanks to DNA testing of saliva on the postage stamp, the US Federal Bureau of Investigation discovered mathematical doctor Theodore Kaczynski, who had been horrifying for a long time in the United States for sending mail bombs to characters. the leader he does not like.

Not only that, DNA also touched history as it brought to light the former US President Thomas Jefferson had an affair with his maid; help identify the remains of the last Tsar and his family. DNA also participated in a famous US scandal: Helping to identify the owner of the "stain" on Miss Monica Lewinsky's shirt, causing its owner - former president Bill Clinton - to publicly acknowledge had sex with this intern.

DNA - the most trusted friend of criminal science

The DNA (Deoxyribo Nucleic Acid) of all living beings is nearly the same; The only difference between individuals in the same species is the sequence of base pairs. There are billions of base pairs in each person's DNA, so the sequence of bases in each person is not the same. So there is no one who resembles the genetic structure of DNA, except for twins with eggs. As a result, DNA became a great " detective ", a great potential tool against crime.

DNA structure remains unchanged throughout life; can be taken from tissue that has been destroyed, burned badly, scavengers buried long . Just one hair, one feather, one piece of skin, cigarette butts, saliva, fluid. . is enough to test DNA.

In about 60% of criminal cases, perpetrators leave traces of DNA. According to professor of criminal law Ronald Allen, Northwest University, DNA is more reliable than any other evidence, as long as we have a good sample and a standard laboratory. If those conditions are enough, DNA is undeniable evidence.

DNA is unique in each person (Photo: whitehouse)

The US Federal Bureau of Investigation is the first agency to consolidate millions of DNA samples into a database. Soon after, the courts of many countries around the world demanded to take DNA samples from all suspects to establish DNA data banks. The bank will support the investigation process, including old cases that cannot identify suspects but have DNA at the scene (especially in rape cases where suspects are strangers). This makes the type of DNA evidence more ' heavy '.

The principle of DNA identification is very simple. The investigating agency only needs to take the DNA samples obtained from the site's traces compared with the stored DNA samples or with suspicious samples. Each DNA sample is like a license plate, one can rely on registration documents to confirm the owner of the vehicle. The other is that DNA cannot be faked in any way.

DNA also causes damage

In fact, DNA testing as well as any scientific analysis is somewhat uncertain, never 100% accurate (the wrong ratio of this technique, in theory, is less than a trillionth ). Therefore, no DNA testing is considered to be the final result and the only evidence to convict.

Indeed, besides the spectacular victories, DNA testing also caused serious mistakes. In 2004, Brandon Mayfield, a practicing lawyer in Portland (USA) was arrested by federal police on suspicion of a bomber on a tram in Madrid (Spain) a few months earlier. The reason for suspicion is simple, American police found his DNA coincided with the DNA samples taken from the scene in Madrid. A forensic expert confirmed that the coincidence is correct.

However, Spanish police claim that Brandon is not the culprit and the DNA comparison results may be wrong. Spanish police continue to investigate and found another man with a DNA profile coinciding with the DNA samples taken from the scene. Through interrogation, this person confessed to being the culprit. US police admitted wrong and Brandon was released.

Brandon Mayfield is not the only case. When analyzing 86 cases of oath jaw in the United States, the researchers found that 54 cases (63%) were unfairly wronged by DNA testing. Common mistakes in technology and laboratory conditions.

There are also some troubles surrounding the identification of criminals by DNA because it involves morality, touching the honor and dignity of the individual. For example, in the case of many suspects, but the police have no evidence that they are involved in the case, are they entitled to sample and test all their DNA? This is a very controversial issue and is not completely consistent in the legal system of many countries.

Perhaps the question will not be asked if everyone's DNA is available on file. Recently, a top British police officer proposed to implement this option, but was opposed because no one could be sure that the personal DNA profile was not abused.