A person who relies on DNA identification technology to find the real criminal.
20 10 Dongtou Village, Penglai Town, Wenchang City 13-year-old girl with mental retardation Xiaoqiu (a pseudonym) was raped and pregnant, and her mother Liang reported the case to the police. After five months of continuous investigation, Wenchang police investigated more than 200 suspicious persons, and finally locked the suspect Long through DNA detection technology. After 24 hours of staying overnight, the suspect was arrested and the "20 10.5. 14" Penglai rape case was successfully cracked. The cases I am looking for are all relatively new. )
In criminal investigation, the primary function of DNA identification technology is to identify criminal suspects and find out the real murderer. DNA technology is the basis for determining the existence of individuals. Everyone's DNA is different. Compared with the previous evidence in court, it can directly prove whether the suspect is related to criminal behavior. In this case, because the victim's intelligence is low, he can't identify the criminal suspect, and there are many criminal suspects, so it is difficult to find the real murderer at the moment. Through the effective use of DNA identification technology, the police successfully locked the suspect and greatly saved the manpower and material resources needed for investigation. At the same time, in the face of irrefutable expert conclusions, criminals can easily bow their heads and confess their crimes.
B relies on DNA identification technology to identify the body, thus providing clues for solving the case.
In June 2009 165438+ 10 10, Guangxi Xiangzhou County Public Security Bureau found a body in the local countryside. About a week ago, the deceased was beaten to death by an instrument. Because the body is highly decomposed, it is difficult to identify. The list of more than 10 missing persons provided by the local people was carefully checked by the task force, and was finally eliminated one by one because of their inconsistent identities. Just as the police were fully investigating, a villager in Liujiang County called and said that his son Qin had been engaged in bus management, and his bus had been resold in the used car market, and the person had been missing for many days. The task force immediately rushed to Liujiang County to let Qin's family identify the photo of the body, and extracted the biological samples of his parents for DNA comparison to determine that the body was Qin. However, Fu Qin and other family members don't believe the appraisal results. Because Qin disappeared on June 4, 2009, the public security organs found the body on June 10, but on June 12, he asked his girlfriend to call his home in Zhongshan City, Guangdong Province, saying that he was hospitalized and it was not convenient to answer the phone. On June 5438+03 and June 5438+04, he also used QQ to chat with his younger brother, saying that his car had been sold and he was now working outside to reassure his family. After investigation, it turned out that the murderer was Huang, a friend of the deceased. On the evening of June 4th, 2009, 165438+ Qin discussed selling his Wuling van to Huang. That night, after drinking in a bar in Liuzhou, they quarreled about selling cars. Huang picked up a claw hammer in the car and slammed Qin's head continuously, causing Qin to die on the spot, and drove the body to a mound next to a sugarcane field in a village in Xiangzhou County in the night. 165438+1On October 7th, Huang sold Qin's car to a boss who operated a second-hand car in Liuzhou, and got 24,000 yuan. 1October11October, Huang fled to Zhongshan City, Guangdong Province, Shaanxi Province, and contacted his family with the phone card and QQ of the deceased in an attempt to conceal the truth. (Ha ha, this case is a bit long, but it is very convincing. )
If it is difficult to identify the source of the body in the murder case, it will naturally make it difficult for the investigation organ to find out the truth according to the identity and social relations of the victim, so as to find out the case. In the above example, if there is no DNA technology, the identity of the body will never be confirmed. Coupled with all kinds of fantasies (Huang contacted his family in the name of Qin), Huang's murder behavior is really likely to hide the sky. There are frequent cases of vicious homicide, especially some cases of dismemberment. In this kind of cases, the victim's body is not in a complete state, which will inevitably lead to difficulties in the identification and appraisal of the victim's identity, and DNA technology enables the victim's identity to be ascertained in this kind of cases. Investigation practice shows that once the identification of the source of the corpse is successfully solved, the investigation work will often turn around, which plays a vital role in the timely detection of the case.
C relying on DNA identification technology can correct misjudged cases and unjust cases.
On the evening of April 3, 2000, two female students living in Baoziwan Township Middle School in Xinrong District, Datong City, Shanxi Province were raped by a gangster in their dormitory. A week after the incident, the criminal police team of Xinrong District Public Security Bureau began to put on record for investigation, and the police handling the case gradually targeted Li Fengchun, a teacher of the school. The main evidences are as follows: Li Fengchun is a private teacher in Baoziwan Township Middle School, who is familiar with the school situation and surrounding environment; On the day of the incident, Li Fengchun has been near the girls' dormitory; Li Fengchun's blood type is type A, which is the same as the sperm left on the mattress surface of the victimized female student. Li Fengchun refused to plead guilty, but he was still in criminal detention. The lawyer entrusted by Li Fengchun insisted on sending samples such as tiny spots on the mattress surface to the Physical Evidence Identification Center of the Ministry of Public Security for DNA technical identification. After two appraisals, the truth finally came out: the two tiny spots on the mattress surface were not left by Li Fengchun. After being wrongly imprisoned for 34 1 day, Li Fengchun finally relied on DNA identification technology to clean up his unjust prison.
In western countries, DNA identification technology has become an important way to identify innocent criminal suspects, defendants and those who have been convicted and sentenced. In our country, there is a broad space for using DNA technology to reverse a case. In order to solve a murder and rape case, we should not only use the general case detection methods, but also pay special attention to correctly analyze the objective attributes of biological material evidence on the spot, because the latter is direct evidence, which can directly prove whether the suspect is guilty or not. In the above cases, all the evidence pointed to Li Fengchun, but in the end, the grievances were immediately clarified through DNA identification technology, thus avoiding the occurrence of long-term detention. Therefore, in some criminal cases that are full of doubts and protracted, it is of great significance to use DNA technology to confirm the real murderer to avoid misjudged cases and unjust cases.
I finished writing DNA identification technology this morning, and I will help you finish the last two questions tonight or tomorrow.
2 the application of trace material evidence in criminal investigation
A In the absence of traditional macroscopic material evidence, microscopic material evidence can effectively lock the criminal suspect.
June 5438+1October 65438+April 2009, a Buick car was parked on a tractor road in Longquanyi District, Chengdu. The 46-year-old driver was lying in the car, covered in blood and without breathing. Because the Buick was abandoned on the tractor road in a remote village, there were no witnesses and other physical evidence, and the only thing that could confirm the identity of the murderer was the traces that might be left on the car. According to the traditional way of solving crimes, it will take a lot of manpower and material resources to drag the car back to the police station to find physical evidence separately. Using imported fingerprint detection equipment, the police opened a tent-like "large space fingerprint fumigation system" in the open space and drove the car in. After more than two hours, two sweaty handprints on the metal pole of the driver's seat of the car stood out. Soon, the 22-year-old suspect Zhang, who was controlled in advance, was locked, and the robbery and murder case was quickly cracked.
As crimes become more and more intelligent and concealed, it is more and more difficult to collect material evidence. Criminals will inevitably try their best to hide and destroy material evidence while committing crimes, which will bring difficulties to the detection of cases. However, according to the theoretical basis of trace material evidence-the principle of material exchange, that is, as long as two objects are in contact with each other, under the molecular interaction between the objects, material exchange will inevitably occur on the contact surface. In the above example, although there is a lack of physical evidence, the discovery of two sweat fingerprints is enough to prove the connection between the suspect and the case, making the suspect's deception futile. For example, in other cases of murder, robbery and rape, the collection of trace material evidence can often provide unexpected clues for investigation.
Determine the temporal and spatial characteristics of the case and the tools used to restore the crime scene.
On February 14, 2003, the office building of Beijing Traffic Law Enforcement Corps was shot by unknown people, and the glass windows of eight offices were broken. According to the evidence provided by the criminal investigation technical department, the targets of these shootings are all windows facing south, and the shooting location should be in the building on the south side of the scene. According to the measurement of shooting trajectory by experts from the Institute of Criminal Science of Beijing Public Security Bureau, the suspected shooting point was finally locked in the homes of four households on the fifth to eighth floors of Building 75 1 Gate. Finally, Yang Liming, who lives on the 6th floor, fell into the French Open. He confessed that after drinking, he shot 10 at the opposite building with a small caliber pistol he carried with him.
On June 7, 2008, a bloody case occurred in a vegetable market in Chengdu. Bing Wang (a pseudonym), a 42-year-old housewife, was stabbed with a fruit knife by a thief who stole a bag. Three days later, Bing Wang died in the hospital ... The police arrested the suspect Zhang Xing (a pseudonym) according to the identification of witnesses, and found a fruit knife for committing crimes from the underground passage of his home. Cunning Zhang Xing originally thought that after the fruit knife was thrown into the hand, the traces of crime would be completely washed away. He never expected that the physical and chemical room of the Criminal Investigation Bureau detected a fur fiber thinner than the hair on the fruit knife through infrared analysis chromatograph, and confirmed that it was the victim's, which made Zhang Xing's criminal facts very clear.
The above two cases prove the application of trace evidence in criminal investigation from the angles of crime time and space, crime tools and so on. In some criminal cases, such as rape, murder and shooting, there may be more than one crime scene. For this kind of case, the analysis and inspection of the trace material evidence on the spot is helpful to determine the original scene of the case, infer the occurrence process of the case, and thus solve the case. In the first shooting, the scene where the glass window was smashed was only the place where the murder happened. Finding the real shooting place of the murderer is the key to solving the case. Experts accurately locked the shooting location with ballistic measurement, which made this seemingly clueless case come to a conclusion at once. In homicide cases, the detection of criminal tools plays a vital role in solving the case, because the criminal tools are often accompanied by substances that reflect the characteristics of the victim and even the suspect. In the second case, although the fruit knife was thrown into the sewer by the cunning criminal suspect, the biological characteristics of the victim were still detected by high-tech equipment, which made the criminal suspect irrefutable. Although trace evidence mostly belongs to indirect evidence, it is these seemingly insignificant evidence that constitute the evidence chain, which largely restores the crime scene and can solve the case.