Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: back to Park (ID:fanpu2019), author: Li Changqing

The case of Chinese "detective" Li Changyu accused of providing perjury has sparked a heated debate around the world. For forensics, an industry that is highly dependent on science and technology, it does not necessarily require forensic subjective fraud to cause unjust and misjudged cases, and technical defects are also sufficient to cause judges to misjudge-and many seemingly reliable criminal investigation methods that we are familiar with through movies and TV dramas, including fingerprint verification and handwriting checking, actually have huge technical defects.

Written by Li Changqing (M.D., medical practitioner in the United States)

One day in December 1985, Everett Carr, a retired driver from Connecticut, was found killed in his home. Karl is said to have been stabbed more than 20 times, cut his throat and hit his head with a blunt object seven times. After that, two young men were believed to have killed Carl and were each sentenced to more than 50 years in prison. The two young men, who had a record of petty theft several times before, were bad teenagers, but both denied that they had anything to do with the murder.

Although the scene was covered with blood, the police did not find any blood on the two suspects. One medical examiner testified that they detected blood on a towel at the scene, and the suspect may have wiped himself with the towel, so no blood was left behind.

The two young men were released on bail in 2018 and 2019 respectively after serving 30 years in prison, and efforts to prove their innocence continued throughout and after their release. His defense lawyers pointed out loopholes in the detection process and gave some new evidence, such as the DNA found at the scene in 2010 and 2012, which could be the killer, was probably from a woman, and the footprints found at the scene were so small that they did not match any of the suspects. In 2020 the judge dropped the murder charges against the two men. Immediately after that, the two men filed a new lawsuit, taking the medical examiner who was a material witness that year, the eight police officers involved in the case and the local government to court.

This is the Chinese "detective" Li Changyu, who was accused of fraud by the Associated Press and many other media recently. Li Changyu was the medical examiner who found evidence of towels, but he was not as famous as he is today at that time. The judge thought it was an unjust case, for which Li Changyu was responsible, while Li Changyu and her lawyer made it clear that they would continue to defend themselves, and the final outcome is unknown.

This is not the first case in which a medical examiner has been accused of fraud, and it certainly won't be the last. In fact, for forensic medicine, which is highly dependent on science and technology, even if it causes miscarriage of justice, it does not necessarily need forensic subjective fraud, and technical defects can also lead to misjudgment.

Forensic medicine is not necessarily "science" on July 28, major media around the world reported the statement made by Li Changyu and the local prosecutor. According to Li Changyu's statement, the focus of the problem mainly lies in his appraisal of the towel that year. Li said that his job is only to "state my scientific findings in court, determine what evidence to use and ask witnesses what questions are the responsibility of lawyers and judges." the chemical test with blood on the towels did not directly accuse the two suspects of being involved in the case, and he also provided evidence of the suspect's innocence at that time, so even if he was found to be misjudged, he should not be held responsible.

Li testified in court that the stain on the towel was blood, according to the fact that he tested the towel with tetramethylbenzidine at the scene and the result was positive. Tetramethylbenzidine detection is a blood screening technique that reacts with catalase in the blood to produce discoloration. Tetramethylbenzidine test was developed in 1970s as an alternative technology for carcinogenic benzidine experiment. Because of its high sensitivity, tetramethylbenzidine test is still a common technique for blood detection and screening. However, catalase is also present in the blood of some vegetables and animals, so further identification is needed to confirm that the results come from human blood (deterministic tests).

But this is not a major problem. The biggest defect in the detection of tetramethylbenzidine is the destruction of DNA.

Li Changyu's use of this method to detect blood in 1985 is a standard operation. The biggest failure in this case is that the towel was collected by the police without routine deterministic testing. However, DNA identification technology was first used in 1986, and its large-scale application was already in the mid-1990s. Even if there was DNA identification technology, this towel will probably not be able to detect DNA, because, as mentioned earlier, tetramethylbenzidine testing can destroy DNA.

In the field of forensic medicine, the fatal flaw is far from the "blood test" technology. With the development of science, more and more "classic" criminal investigation techniques have been found to be less rigorous.

Because of the frequent occurrence of the situation, at the request of the United States Congress, the National Research Council (National Research Council, NRC) issued a report on forensic science in 2009, pointing out that there are the following major problems in the field of forensic expertise:

Lack of scientific verification technology: many traditional forensic identification techniques lack scientific verification. Many techniques, such as hair identification and handwriting identification, have been widely used in the past, but they have not been fully scientific research and verification to determine their reliability and accuracy.

Subjective tendencies and prejudices of experts: expert opinions in forensic expertise may be influenced by subjective judgment and personal bias. This may cause different experts to draw different conclusions on the same evidence, resulting in inconsistencies in court decisions.

Lack of interdisciplinary cooperation: forensic identification often involves knowledge in multiple disciplines, such as biology, chemistry, physics and so on. However, the lack of communication and cooperation between different disciplines may affect the accuracy and reliability of comprehensive identification.

Lack of training and lack of standards: some forensic forensic personnel lack the level of training and education and lack the necessary professional standards and guidelines of practice. This may lead to non-standard and incorrect application of the technology.

Expression of evidence: the report emphasizes the expression of forensic evidence in court, and expert statements may be too positive or ambiguous, making it difficult for judges and juries to understand and evaluate the reliability of the evidence.

Analysis of several major criminal investigation technologies in the field of forensic medicine, the objective limitations of the technology and the subjective bias and even fraud of individual practitioners often combine with each other (the former gives the latter space), resulting in unjust and false cases. What's more, some criminal investigation techniques have not undergone the most basic scientific test since their birth. The following major "problem" technologies have been or are still regarded as classic means of criminal investigation.

FBI microscopic hair analysis: before 2000, forensics relied on microscopic observations for hair identification at crime scenes. Proponents of the technology claim that specific hair features are related to physical signs such as height. But with the growing skepticism about the technology and the introduction of new mitochondrial DNA identification technology, the innocence Project, a non-profit organization that works for wrongly convicted people, has begun to reverse cases for people previously convicted through hair analysis. In the end, FBI, the US Department of Justice and other organizations jointly reviewed some pre-2000 hair analysis reports and found that most of the 268 reports submitted by FBI as evidence had errors-257, or 96 per cent, were wrong.

The main reason for the unreliability of hair microscope analysis is that many people's hair is actually very similar under the microscope, which makes it easy to connect irrelevant people and convict those who should be innocent.

It is difficult to review how many wrongs and wrongs these unscientific and erroneous forensic reports have caused. In the United States, for example, there were more than 3000 reports that could be traced back to that year, but by March 2015, the FBI had reviewed only 500 of them.

West's bite mark analysis: Michael West, a dentist in Louisiana, has testified to the police as a bite mark analyst in a number of criminal cases. including testimony at the trial of the famous serial murderer Ted Bundy. However, with the passage of time, more and more bite mark analysis has been found to be inaccurate. Including the Bundy case, subsequent studies have shown that bite mark analysis does not prove that Bundy left tooth marks on the victim.

In 2020, a total of 34 charges were overturned because of unreliable tooth mark analysis, including those who had been in prison for decades and even sentenced to death. For example, black Howard, who was arrested in 1992 on charges of murdering a white woman, was sentenced to death for testifying that the victim's tooth marks match his teeth. Fortunately, the 2010 DNA test proved Howard's innocence.

Nowadays, bite mark analysis has been basically regarded as a pseudoscience in the field of forensic medicine.

Handwriting identification: handwriting identification, also known as clerical identification or handwriting identification, is a practice that attempts to determine whether it is written by a particular individual by analyzing handwriting and writing characteristics. In the past, handwriting identification was widely used in forensic medicine and criminal justice system, but it is generally regarded as a kind of pseudoscience in the modern scientific community.

Although there are no large-scale scandals, handwriting identification has been shown to be unreliable in some important cases, such as the Mark Hoffman case. Hoffman is an impostor and clerical forger in the United States. In the 1980s, he produced a large number of forged historical documents and deceived handwriting appraisers at the time. This incident reveals that handwriting identification may be affected by personal misleading or fraud in some cases.

Handwriting identification also caused chaos in the Madrid subway bombing known as 9 / 11 in Spain, which led to the arrest of an American lawyer who had nothing to do with the bombing.

Fingerprint identification: people believe that fingerprint identification is based on the fact that everyone's fingerprints are different, but there is no conclusive evidence for this claim. FBI has done an analysis and found that an error may occur in every 306 fingerprint identification. The Florida survey was even more disturbing, with one error in every 18 analyses. In fact, fingerprint identification experts all know that this technology is not 100% accurate, but because of the perennial influence of movies and TV dramas, once there is a fingerprint identification that the suspect's fingerprints match the scene, it is likely to convict the suspect.

Like handwriting identification, fingerprint identification does not report large-scale scandals, but it also causes trouble for many individuals, sometimes completely unrelated people. In 1997, Ross, a 51-year-old Scot, was killed, and the suspicion soon fell on David, who had worked in her family, and the main evidence of his conviction was fingerprints. But at the same time, two fingerprints were found at the scene, which were identified as belonging to another female police officer, Mikey, who denied that she had been at the scene, and the police at the scene denied seeing her. Because denying the fingerprint identification of the female police officer also means denying the reliability of the suspect's fingerprint identification, the local fingerprint expert firmly believes that it is the female police officer's fingerprint, and the female police officer is also dismissed for perjury. Later, more than 100 experts around the world confirmed that the two fingerprints were not McGee's, and David was acquitted after many years in prison because of doubts about the reliability of the fingerprint identification.

It should be pointed out that some high-precision technologies that are regarded as the gold standard are not unassailable, such as DNA identification technology, which will be affected by sample restrictions, database integrity and other aspects. Expensive testing also limits its application, and a complete DNA identification can cost up to $50, 000.

Since there are so many criminal investigation techniques that are not unassailable, readers will inevitably worry about the impartiality in judicial practice. In fact, the police and judges can never decide a case on the basis of a single evidence, including China. Legally speaking, all material evidence from forensic doctors and other sources need to be verified to form a complete chain of evidence before the parties can be convicted.

Forensic medicine is a science, its development also depends on the development of other disciplines, and forensic identification is also affected by political, judicial and social aspects. Forensic practitioners are afraid of misjudging both the good and the bad. Under such pressure, it is not easy to be completely objective. Today, medicine for the living is far from perfect, and medicine for the dead is certainly not perfect. Scandals and detectives all need to be treated in a normal way.

Reference link

Https://www.criminallegalnews.org/news/2020/nov/15/thirty-fourth-conviction-based-bite-mark-forensics-overturned/

Https://nap.nationalacademies.org/catalog/12589/strengthening-forensic-science-in-the-united-states-a-path-forward

Https://theconversation.com/how-corruption-in-forensic-science-is-harming-the-criminal-justice-system-108975

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