The "silver case" was solved! How to identify a person by DNA technology?

I was surprised to see a British-made film, The Killer's Password, which was adapted from a real British case. The film

The "silver case" was solved! How to identify a person by DNA technology?

I was surprised to see a British-made film, The Killer's Password, which was adapted from a real British case. The film tells the story of the first time that DNA was used to deal with judicial cases. At that time, Britain was 1985. At that time, I suspected the origin of an immigrant child, and confirmed his identity with the help of DNA technology, saving the fate of mother and child being separated artificially. The film focuses on the first application of DNA in criminal cases, which was in 1986. At that time, a confessed man was acquitted in Britain because of the application of this technology, and the real murderer surfaced.

The amazing application of DNA fingerprinting in judicial cases

The film "The Black Boy's Code" reproduces a real criminal case in Britain in detail by using DNA technology (the real names of some parties are hidden in the film): 1983 12/22 At 7: 20 am, the body of Linda Manning (15 years old) was in the grass on the roadside leading to the mental hospital. She was naked from the waist down. It is understood that she was strangled on the way to see a friend the night before yesterday and raped after her death. The semen extracted from the corpse shows that the genetic gene secreted by the murderer is high concentration of phosphoglucomutase's (ICM) A-type H enzyme, which only accounts for 10% of adult males. The investigation was first conducted in a nearby psychiatric institution, Caton Hayes Hospital, but the investigation ended in failure. Later, the police discovered that they actually asked the murderer, but they didn't realize that he was the murderer at that time. 1On the afternoon of July 5th, 986, another victim, Dawn ashworth, disappeared. She is also 15 years old. He is a student in enderby school. Two days later, ashworth's body was found where Linda Manning's body was found. She was torn to pieces, and the scene was creepy. Sperm tests showed that Linda Manning and Dawn ashworth died with the same hand. After Dawn ashworth was killed, Richard barker Lan, a kitchen handyman at Caton Hayes Hospital, was under suspicion. Richard barker Lan is simple-minded, precocious and looks a bit silly. Sometimes he hides in the dark and suddenly jumps out to scare women and young girls, so he has a bad reputation. At that time, the police ruled out his suspicion. In the summer of 1986, the police took him to the police station and interrogated him. After two days of confusing and contradictory confessions, he finally signed the confession and admitted that he killed Dawn ashworth. But empirical blood, he doesn't belong to the person with phosphoglucomutase H enzyme secretion gene type A1986165438+1October 2 1 day. Dr. Ali Jeffrey, a researcher at Leicester Institute, extracted DNA from the murderer's semen and compared it with the blood samples of kitchen handyman. He concluded that Richard barker Lan was innocent. The frustrated police then thought of a way to find a needle in a haystack and planned to conduct a large-scale test on local men. At the beginning of 1987, the police decided to invite young men aged 6 to 34 in this area/kloc-0 to donate blood samples and saliva. After testing, the samples belonging to blood group A/PGM1+Secretary were sent to the technical office of the court of the Ministry of Interior for DNA testing. From 198 1 year 1 to September, 4,583 men were tested, but the police failed. In August 1987 1, four bakery workers gathered in Leicester bar to drink. One of them talked about a man named Colin Picha? Pitchfork employees once threatened him with a blood test. Shy and weak, he used forged documents to collect blood samples in the name of Colin Pitchfork. Another man also mentioned that Pitchfork had promised to give him 200 pounds ($300) if he wanted to take the body double test, but he refused. Pitchfork explained that he was afraid to take the exam because he was accused of indecent exposure and worried that the police would give him a hard time. A woman sitting at a table reported the news to the police. 1987 September19, 27-year-old Colin Pitchfork was arrested in Little Torun. According to the police's computer data, Pitchfork is an exhibitionist and has been to the clinic of that mental hospital. After the police arrested Pitchfock, his blood sample was tested and sent to Jeffrey's laboratory. DNA test results show that he is the murderer who raped and killed Linda Manning and Dawn ashworth. 1988 65438+1On October 22nd, Colin Pitchfork was found guilty and sentenced to life imprisonment.

This film reveals that DNA technology has played an amazing role in identifying real criminals and finding innocent people, and many successful cases have inspired people to use this technology. In the movie "Black Boy's Password"? DNA technology whitewashes a person's criminal suspicion, especially when this person's criminal suspicion is strengthened by his guilty confession, its significance is even more significant. A defendant may confess his crime against his will for various reasons (such as buckland in this case, who is obviously a coward). Without the help of DNA technology, he may be misjudged. Therefore, in the United States, "some States have enacted laws requiring DNA testing after conviction, some States have expanded or abolished laws restricting the scope of application of DNA evidence, and some States are in the process of legislation."

Accurate DNA technology will also have application errors.

In our country, in ancient times, personal identification relied on the old method of blood test, which was not very reliable. However, in ancient times, when China was underdeveloped in science and technology, it became a common personal identification method for judicial organs. Ji Yun's Notes on Yuewei Caotang said: "According to Kerwin Chen's blood, see the Biography of the Sages in Runan, which has been said since the Han Dynasty." Even in ancient times, people have realized that the method of dropping blood is not a reliable method. Ji Yun relayed the old officials' statements and said, "The blood of the same flesh and blood must be consistent, and it is normal to talk about it. Or put a container on the ice and snow in winter, which is extremely cold; Or Xia Yue wiped the vessel with salt and vinegar to make it taste sour and salty: then the dripping blood would coagulate when it entered the vessel, although it was not suitable for the next of kin. Therefore, it is not enough to drop blood. " Because personal identification plays an important role in many cases, if the identification is wrong, the identification and handling of the case is likely to be wrong.

At present, personal identification depends on DNA detection, and DNA identification technology (also known as DNA fingerprinting) is recognized as a relatively accurate technology, which is considered indisputable in personal identification. Some people say that the discovery of DNA is a milestone in science and a century symbol in the history of science. The application of DNA in criminal justice is also revolutionary. Commenting on the application of this technology in American criminal justice, American philosophy professor Susan haack said: "When DNA was first identified as genetic material half a century ago, who would have thought that DNA analysis would now play such a role in the criminal justice system and the public's understanding of the law? Even 20 years ago, forensic scientists could only determine whether the blood sample was human or animal, male or female, and if it was human, what blood type it was-among Americans, 3% had the least blood type and 43% had the most common blood type. DNA analysis makes it possible to identify more accurately (it is said that the possibility that the stains on Lewinsky's skirt randomly match Clinton's semen is one in 7.87 trillion). The United States introduced it into criminal cases for the first time in 1986, which made the power of judicial justice quite amazing. By the spring of 2002, DNA tests proved that 100 prisoners were innocent, including a considerable number of death row inmates.

However, law enforcement officers and judicial personnel have enough vigilance against their own cognitive ability, and at the same time they have to accept expert opinions formed by all scientific and technological means without vigilance. There are two main methods for DNA identification: one is STR typing, usually called DNA detection, which can identify individuals and identify the same person; The second is mitochondrial DNA sequencing, which can not be identified by the same method, but can only be used for negation, not for affirmation. If you don't understand the basic knowledge of DNA testing, you may make mistakes in choosing evidence. Even more deadly, although DNA technology is a relatively accurate technology, the appraiser lacks a sense of responsibility, the appraisal work lacks accuracy, and even caters to the entrusting party to provide its expected opinions. No matter how precise the technology is, it may not guarantee an accurate conclusion. In the United States, Wilma Pang Sai and her two-year-old daughter were stabbed to death in the Castro case of 1989, and the suspect Castro was arrested. The police found blood on his watch, and the DNA map of the blood was consistent with that of the victim. However, in the preliminary examination of this case, many mistakes were found in the experiment process: no species experiment was carried out, no redundant bands were reported, and the daughter's test results showed that there were redundant unreported bands. Contaminated probes were reused but not recorded, bands with a difference of more than 3 times standard deviation were still marked as matching, blind inspection was not carried out as required, negative control was not used or the source of control samples was not recorded. These factors lead to the loss of evidential ability of DNA evidence.

In China, many DNA detection errors have also been found, which have aroused widespread concern in society, including Li Jiuming of Hebei and Yue Tuyuan of Shanxi. There are other cases that are not as well known as these cases, and mistakes in DNA identification have also been found. For example, there was a bizarre case in Xinjiang: on July 13, 2004, Lei disappeared, and his family alerted the local police station, and then published "Looking for You" in the newspaper. At noon on July 24th, Lei's sister received a phone call from a stranger saying that a man's body had been found in a canal in Halayugong township. Because no one reported it, it has been buried, and the appearance of the deceased is similar to the photos published in the newspaper. Hong Lei immediately contacted the Korla Public Security Bureau to identify the body. The body was soaked in water and deformed. After being buried underground, it is covered with mud. It's hard to identify when it's dug up. After seeing the body, Lei Wufu, Lei's father, thought his hairstyle was really similar, but it was difficult to determine whether it was his son. The police dissected the body that night, and the Korla Public Security Bureau also informed Lei Wufu to draw blood from the unknown body for DNA identification. On August 24, 2004, the Notice of Appraisal Conclusion issued by the Public Security Bureau of Korla City stated that "the blood samples of the unknown corpse and Lei Wufu were identified by DNA and stomach contents, and the appraisal conclusion was that the unknown corpse was related to Lei Wu, and the cumulative paternity probability was 99%, and there was no toxic substance in the stomach of the unknown corpse". On August 30th, Lei Five Blessingg officially received the Notice of Appraisal Conclusion from the Public Security Bureau of Korla City, and the conclusion was "drowning death". However, the police did not come to the conclusion that ray was killed by him. On September 3, 2004, the Criminal Investigation Detachment of Bazhou Public Security Bureau issued a death certificate and a cremation certificate after forensic identification again, and the body was cremated. Hong Lei suspected that his brother's death was related to a woman named Xin Wei, so he asked, "My brother can't swim. How could he drown?" From Lei's cell phone records, it is found that Lei did look for him on the night of the accident, and no one has seen him since. Hong Lei submitted a document to the Korla Public Security Bureau, asking the police to investigate. On September 19, 2004, Xin Wei underwent plastic surgery in Urumqi, preparing to flee with her mother, and was arrested by the Public Security Bureau of Korla City. Xin Wei's father was also arrested in Golmud, Qinghai. To the police's surprise, they not only confessed the fact of killing Lei, but also told the location where the body was buried. On June 9, 2004, 10, the police dug up the body in a Gobi desert on Kuweigong Road and informed Lei Wufu to take blood samples. Ray's mother was also given a blood sample. Lei Wufuhe also participated in the identification of the clothes of the deceased, confirming that the white T-shirt, black pants and black shoes were all worn by Lei when he went out that day. Besides, one of Ray's red ropes is there. From June 5, 2005 to1October 6, 2005, the Public Security Bureau of Korla City issued the Notice of Appraisal Conclusion, which concluded that the base sequence of the HV region of mtDNAHV of Lei's corpse was consistent with that of his mother Shi Changhui. The identification conclusion is that the body is thunder, thus denying the previous statement that the male body is thunder. Why are the two bodies identified as the same person? The Korla Public Security Bureau claimed that it was a machine failure, and later said that the sample was contaminated.

Why is there an error in DNA testing?

The reason is that the technical method itself may be wrong. Susan haack warned: "Police and laboratories may make mistakes. For example, sometimes samples are not presented blindly, but in the form of expecting empirical evidence. In addition, DNA analysis has greater certainty in excluding suspects than in identifying criminals, and identifying the latter sometimes requires vigilance assumptions about reference categories. Therefore, it is not surprising that DNA evidence is not only a powerful tool to prove innocence and find guilt, but also a very confusing possibility (as Simpson told us all). " Errors in DNA technology, together with other factors, will almost inevitably lead to errors. There are three main factors:

First, the inspection materials are contaminated. Due to the negligence of sample storage, the detection based on contaminated samples will inevitably deviate from the truth, resulting in the error of detection results. Susan Susan haack pointed out: "Assuming strict testing, an innocent defendant will not have the same DNA as the criminal, but a low possibility that cannot be ignored is that the laboratory is wrong or the sample is contaminated."

Second, appraisers provide catering appraisal opinions. DNA testing, like other appraisals, should be scientific and not "friendly appraisal", but the appraisers belong to the entrusting party or the same system with the entrusting party, and long-term acceptance of the fixed customer relationship of the same entrusting unit will make individual appraisal institutions and their personnel lose their scientific spirit, thus providing appraisal opinions that cater to the entrusting party or the entrusting party's wishes. Unfortunately, it is not the only phenomenon that appraisers do not follow objective reasons, and the testing room has become more than one place to process evidence. When the appraiser no longer has the inherent scientific spirit, "scientific evidence" is no longer scientific.

The third is human error. On June 23, 2003,165438+1October 23, an expert admitted that there were many problems in DNA identification in some areas of China, which restricted the safe and effective use of this technology. Although DNA technology is highly accurate, it cannot be automatically converted into objective evidence, and it needs appraisers to sample, experiment, compare, analyze and interpret to get the results. Errors in any of the above links may reduce the accuracy of DNA evidence, which will not only help to confirm the truth, but will lead to misjudged cases. In addition, some people deliberately arranged to confuse the case handlers and induce them to draw wrong conclusions. What is even more worrying is that some people use DNA technology to excuse themselves. In Milwaukee, USA, antonin Turner was accused of rape and was detained pending trial. During his detention, another murder happened outside the prison. The evidence collected by the police proves that the DNA patterns of the physical evidence in these two cases are exactly the same. It seems that antonin Turner is innocent. It was later found out that antonin Turner sent a semen sample out of prison, and his relatives paid a woman $50 to claim that she had been raped and raped by many people in one day. Anthony Turner tried to mislead investigators in this way and win his acquittal. The transfer of DNA can not only excuse itself, but also frame others. Unintentional transfer can also lead to innocent people involved in litigation. If the investigators lack insight and blindly listen to the opinions of DNA experts, it may lead to the result of misjudging innocent people or conniving at criminals.

Fearing that the jury was misled, a Canadian judge "refused to let DNA experts prove the possibility of random matching-fearing that the jury would convict the defendant only on this possibility, rather than considering it with other evidence". However, more people are superstitious about DNA evidence. In our country, until now, the voice warning that DNA identification may be wrong is not loud enough, and the misjudged case lurks in superstition and blind obedience to this "scientific evidence". Eriocheir sinensis believes that all the DNA of residents living in China can be registered in the public security system, and no matter what cases, they can be easily solved.