The crime scene is the key breakthrough point in collecting evidence, that is, in criminal investigation:

The scene is the main place where evidence is collected. It is where the investigators conduct investigation and investigation in accordance with the law in order to ascertain the facts of the case. Work to obtain various evidence materials related to the facts of the case. Collecting sufficient and reliable evidence is the prerequisite for judicial organs to analyze and study the case, and is the basis for correctly identifying the case and handling the case. Collecting evidence is a basic skill for criminal investigators, and it is also a concrete manifestation of the ability to handle cases and professional quality. When handling cases, investigators must firmly establish evidence awareness and always regard the collection, verification and improvement of evidence as the central link in handling cases.

1. Firmly establishing a correct awareness of evidence is the basis for handling cases in accordance with the law

Evidence is the basis for ascertaining the facts of the case. It is a specific problem that case handlers often encounter, and it is also the basis for criminal cases. key to the success or failure of litigation. To this end, a correct awareness of evidence must be firmly established.

Evidence, as the name suggests, is the basis for proof. When parties use known facts to infer unknown facts, the unknown facts are the object of proof and the known facts are evidence. Legal evidence is not completely equivalent to the evidence in people's daily life. It is the material used by judicial personnel to ascertain and prove the facts of the case, and is subject to adjustments by legal norms. The "Criminal Procedure Law" stipulates: "All facts that prove the true situation of the case are evidence." "Judges, prosecutors, and investigators must follow legal procedures to collect evidence that can prove the guilt or innocence of the criminal suspect or defendant, and the circumstances of the crime. It can be seen that criminal evidence is all objective facts collected and reviewed by judicial personnel in accordance with the law to determine or deny the facts of a crime, prove the guilt or innocence of a criminal suspect or defendant, and the severity of the crime. Evidence has three basic attributes: objectivity, relevance and legitimacy. The objectivity and relevance of evidence are the content of evidence and the essential attributes of evidence; legitimacy is the form of evidence and the guarantee of objectivity and relevance.

Evidence always exists in some form. The "Criminal Procedure Law" stipulates: "There are seven types of evidence: (1) physical evidence and documentary evidence; (2) witness testimony; (3) victim's statement; (4) confession and defense of criminal suspects and defendants; (5) identification Conclusion; (6) Inspection and inspection records; (7) Audio-visual materials. "Physical evidence is all items and traces that can prove the facts of the case. It proves the case based on the external characteristics, existence conditions and material attributes of the items or traces. It has strong stability and authenticity. Documentary evidence is written material that uses words, symbols, graphics, etc. to express ideas and recorded content to prove the case. Witness testimony is a statement made by a witness about the facts of the case that he or she has heard and witnessed. It is generally in the form of an oral statement, or it can be written by the witness himself or made by the case handler to make an inquiry transcript. The victim's statement is a statement made by the victim about the fact that he was harmed by a crime and what he knows about the criminal suspect. The confessions and defenses of criminal suspects and defendants are the explanations and confessions made by criminal suspects and defendants regarding the facts of the case. The appraisal conclusion is a written conclusion made after the investigative agency assigns or hires a person with specialized knowledge to appraise certain specialized issues that need to be solved in the case. Inspection and inspection records are records produced by investigators after conducting an inspection of crime scenes, persons, and corpses, and also include drawings, photos, etc. Audio-visual materials are materials that prove the facts of a case using information stored in audio recordings, video recordings, photographs, computers or other high-tech equipment. Only by correctly understanding the legal form of evidence can we correctly collect and review evidence during case handling and improve case handling efficiency.

When handling cases, we often encounter the question of how far evidence must be collected to meet the requirements of litigation. The "Criminal Procedure Law" stipulates: "In cases that have been concluded by the public security organs, the criminal facts should be clear and the evidence is reliable and sufficient." The clear facts of the case are requirements for the degree of identification of the object of proof, that is, the facts and facts related to conviction and sentencing. The circumstances include whether the criminal act was committed by the criminal suspect, the time, place, means, consequences, purpose, and motivation of the crime, as well as the criminal suspect's own situation and post-crime performance, etc. The evidence is reliable and sufficient, which is a requirement for the adequacy of the basis for proof. It includes two requirements: the evidence is reliable and the evidence is sufficient. The so-called evidence is reliable, which means that each piece of evidence on which the case is decided is objective and relevant upon investigation, and can prove the true situation of the case. This is a requirement of the quality of evidence. Sufficient evidence means that the evidence in the entire case has sufficient probative power on the facts of the case and is sufficient to prove the true situation of the case. It requires that the evidence in the entire case can form a complete evidence system that is interconnected and corroborated with each other, and constitutes a sufficient basis and reason for determining the facts of the case. Sufficient evidence is a requirement for the amount of evidence. Evidence certainty and evidence adequacy are interdependent and inseparable organic wholes. In practice, the criteria for examining whether the evidence is sufficient and reliable are: first, every piece of evidence used to decide the case is verified to be true; second, the evidence is related to the facts of the case and can play a role in proving the case; third, the case is The facts and circumstances are corroborated by corresponding evidence; fourth, there is no contradiction between the evidence and between the evidence and the facts of the case; fifth, the evidence in the entire case forms a complete evidence system, and the conclusion is unique and exclusive.

2. Practicing the basic skills of evidence collection is a guarantee for handling criminal cases

Collecting evidence includes discovering evidence and extracting evidence, which is the core content of investigation work. Discovery of evidence is the use of certain methods and means to find or reveal evidence materials related to the case. Extracting evidence is the use of certain methods and means to obtain or admit discovered evidence materials. Discovering evidence is the prerequisite for extracting evidence, extracting evidence is the purpose of discovering evidence, and discovering evidence is always for the purpose of extracting evidence.

Collecting evidence is a very legal and practical work. In order for the evidence collected to be legal and effective, it is necessary to adhere to regulatory requirements when collecting evidence. First, the procedure is legal. Case handlers are strictly prohibited from extorting confessions through torture and collecting evidence through threats, inducements, deceptions and other illegal methods. Evidence obtained through illegal methods cannot be used as the basis for finalizing a case. Second, it is objective and comprehensive. Authenticity is the core of evidence, which requires opposing subjectivity and one-sidedness in the collection of evidence. Everything should be based on the objective actual situation. We can neither use subjective guesses to replace objective facts, nor collect evidence according to subjective needs, nor can we use fraud to forge evidence. The third is to rely on the masses. Criminal suspects are surrounded by the masses, and traces and evidence of criminal acts are around the masses. Case investigators can only achieve their desired goals by going deep among the masses and relying on the masses to provide clues and information. Fourth, it is prompt and timely. Collecting evidence quickly and timely can not only improve the efficiency of collecting evidence, but also improve the reliability of collecting evidence. The fifth is to focus on the use of modern scientific and technological means. With the rapid development of science and technology and the improvement of the scientific and technological level of the entire society, criminal methods are also constantly changing. Intelligent crimes using high-tech means have become a very prominent problem. We must adapt to the needs of the new situation, pay special attention to the full use of modern science and technology and means when collecting evidence, and effectively ensure that crimes are accurately and timely exposed, confirmed and punished.

Evidence is the record or reflection of past events in the human brain or material carrier. It is often concealed. Some criminal suspects cover up the facts of the case and hide the evidence of the case, which further strengthens the evidence. of concealment. In addition, over time, memories fade and physical traces disappear, making it difficult to find evidence. However, the existence of the case is objective, and the evidence materials are also objective. As long as the method is correct and the work is meticulous, evidence related to the case will be discovered. The first is to correctly delineate the search scope. When case handlers delineate the scope of investigation, they actually determine the scope of evidence collection, because the purpose of determining the scope of investigation is to find criminal suspects and collect evidence materials. At the same time, the criminal suspect’s confession is also a type of evidence. The second is to be good at discovering evidence. After delineating the scope of investigation, every effort must be made to discover evidence. When handling a case, sometimes evidence can be discovered directly, and sometimes evidence needs to be discovered through various links. Discovering suspect clues is also an important way to find criminal suspects. The third is to pay attention to finding evidence materials. Evidence clues are not equal to evidence materials. If someone has possession of documents and items related to the case, it does not mean that he has mastered documentary evidence or physical evidence. Some insiders are unwilling or afraid to admit that they understand the case or have items related to the case. Case investigators must use appropriate methods and strategies to find out the situation based on evidence and clues.

There are many ways to extract evidence, and many of them require the use of natural science technologies and methods such as chemistry and physics. Commonly used methods for obtaining evidence include: First, the transcript extraction method. This is a method of extracting evidence materials in the form of written records. It is mainly suitable for extracting evidence materials that contain words, activities, and states. Its forms include interrogation transcripts, interrogation transcripts, on-site investigation transcripts, physical evidence inspection transcripts, and human body examinations. Transcripts, identification transcripts, etc. The second is the audio and video extraction method. This is a method of extracting evidence by means of photography, audio and video recording. It is mainly suitable for extracting various physical evidence, documentary evidence, and evidence containing sounds and images, among which photography is the most widely used. The third is the physical extraction method. This is a method of directly extracting items, documents and trace carriers related to the case. It is mainly suitable for small physical evidence and trace carriers, as well as various documentary and audio-visual evidence. The fourth is model extraction method. This is a method of extracting evidence by making models, and is mainly suitable for various three-dimensional trace evidence. For example, three-dimensional fingerprints, three-dimensional footprints, tool marks, etc. can be extracted using the model. The fifth is the paste extraction method, which mainly uses pasting, copying, adsorption and other methods to extract evidence. It is suitable for all kinds of flat trace evidence. When extracting evidence, attention should be paid to scientificity and legality. The value of the evidence should not be damaged due to improper extraction methods, nor should it be extracted by illegal means, otherwise it will lose its probative power.

Collecting evidence is a scientific and practical knowledge. Case handlers must not only have a solid theoretical foundation, but also have rich practical experience. The specific methods include: First, ask. Inquiry is an activity to learn about a situation through conversation or questioning. It is a method used in any case to collect evidence. The main target is witnesses. The second is interrogation. Interrogation is an essential evidence collection method in criminal cases, and its objects are only suitable for criminal suspects and defendants. The third is identification. Identification is a method used in many cases, and the identification conclusion and related testimonies and transcripts can be used as evidence. The fourth is inspection.

Inquest is an evidence collection method used in many cases, and its objects are generally the places, objects and bodies related to the case. From the perspective of collecting evidence, inquest has a dual meaning. On the one hand, inspection is an important way to discover and extract various physical evidence; on the other hand, inspection itself is also a form of evidence. The fifth is inspection. It is an evidence collection method mainly used in cases related to human condition, such as human injury cases and liability accident cases causing human injury. Sixth is search. It is an evidence collection method mainly used in criminal cases. The object of search can be a place, a person, a vehicle or other objects. Seventh is experimentation. Experiments are also called investigative experiments, and experimental records are the main form of evidence. Eighth is identification. The objects of identification can be diverse, they can be physical evidence or documentary evidence; they can be human bodies or corpses. These methods can be used not only to collect evidence, but also to ascertain the facts of the case and review and judge the evidence.

3. Taking the crime scene as the core is the top priority of the evidence collection work

The crime scene is where the suspect violated a certain object at a certain time and space in order to commit the crime. A place that causes a series of changes in a specific physical environment. Specifically, the crime scene is the place where the crime occurred and other places where traces and physical evidence related to the crime are left. Generally speaking, there is only one scene for a case, but sometimes there may be multiple scenes. The crime scene objectively reflects and records the criminal activities, which is a reliable basis for confirming the crime and an effective means and method for discovering clues to the case.

According to materialist epistemology, as long as a criminal case occurs, there is a crime scene. Crime is inseparable from specific time and space. Once a criminal act occurs, the criminal information is stored in the relevant object as a result of energy exchange. A crime scene is a specific place where a criminal suspect commits a crime. Therefore, the crime scene stores and transmits crime information. If a criminal suspect commits a murder crime in a certain place, the suspect's fingerprints, footprints, blood stains, odors, and weapons, clothing, documents, etc. left at the scene may be left on the scene. These traces and objects present at the scene convey to people the criminal information of murder. It is precisely in this way that investigators can capture these criminal information through on-site investigation and on-site visits, thereby analyzing and portraying the "image" of the criminal suspect, correctly determining the direction and scope of the investigation, and finally catching the criminal suspect. At the same time, it is also the main way to obtain the main evidence to prove the facts of the case.

After a crime occurs, investigators in most cases do not know who is the perpetrator, and whether the items and traces at the scene are intrinsically related to the case. The direction and scope of the investigation work can only be determined through inspection and inspection of the scene conditions and analysis and judgment of the traces and items left on the scene. For this reason, the investigation must be comprehensive and meticulous, and more trace evidence must be collected to lay a good foundation for solving and handling cases. Obtaining evidence must be done in accordance with procedures, that is, in accordance with legal provisions. Otherwise, the evidence collected cannot be used as a basis for determining the facts of the case. The on-site investigation records, on-site drawings, and on-site photos should be consistent with each other, and should not be inconsistent with each other. If there are conflicts, they must be reasonably eliminated. Otherwise, doubts will arise and the proof will be lost. Regarding the traces and items extracted from crimes, we must seek truth from facts and extract whatever is available and cannot make arbitrary choices.

4. Taking the parties’ words as clues is an important way to obtain evidence

Some criminal suspects are very cunning and leave no traces or items at the crime scene, and some do not leave traces or items at the crime scene for other reasons. Valuable trace evidence was recovered from the crime scene. This requires more work to be done to obtain confessions from criminal suspects, statements from victims, and testimony from insiders.

First, we must work hard on interrogating criminal suspects. First, collect evidence from the facts confessed by the criminal suspect. If the criminal suspect confesses the crime, use his confession as the main line to collect evidence to prove the crime. Secondly, collect evidence from the plot confessed by the criminal suspect. Some of the plots told by criminal suspects when confessing their crimes may not be directly related to the crime, but they can prove the authenticity of the criminal suspect's confession. This can make the evidence system more complete and prevent criminal suspects from retracting their confessions. Again, collect evidence from clues provided by the suspect. During the interrogation process, criminal suspects sometimes do not remember the plot and details clearly, or have delusions due to objective reasons. They often provide some clues about the plot or details of the case and crime. These clues are the direction in which investigators collect evidence. Fourth, collect evidence from the suspect’s defense. There are basically three possibilities for a criminal suspect's excuse, namely true and false, and some are true and some are false. If the evidence collected can prove that the facts and circumstances defended by the criminal suspect are true, it will be very helpful in finding out the facts; if it is false, or there is some truth and some falsehood, it can also prove the criminal suspect's attitude.

Second, we must make a fuss about digging out the victim’s statements. The victim is the main party in a criminal case and the object of criminal infringement. The victims in most cases have a certain understanding of the crime and can provide information related to the crime. Therefore, the victim's statement plays an important role in correctly determining the direction of the investigation, collecting and verifying evidence, and correctly determining the facts of the case. First, collect evidence from the victim’s statement about the parts of the body that were violated.

Judging from the experience of investigation practice, the injured part is an important way to collect evidence. Criminal suspects are prone to leave fingerprints, footprints and other traces of crime at the injured part. Secondly, evidence is collected from the victim’s statements about the suspect’s manner and method of committing the crime. The victim is the object of infringement. Under normal circumstances, the victim is relatively clear about the criminal suspect's method and method of committing the crime. The manner and method of the suspect's crime stated by the victim are important clues for investigators to collect evidence. Again, collect evidence from some special circumstances stated by the victim. Only the victim and the suspect know about this special situation. Some of these situations are intentional actions by criminal suspects, and some are unintentional actions. For example, the suspect's clothes were torn when he fled the scene of the crime. Fourth, collect evidence from the victim’s statements about the consequences of the violation. The consequences of the crime committed by the criminal suspect, such as the extent of the injury, the items robbed, the property defrauded, etc. Fifth, collect evidence from the characteristics of the suspect stated by the victim. Collect evidence of the suspect's physical characteristics, such as height, body shape, dialect and accent, clothing, etc.; collect evidence of the suspect's movement characteristics and signs of struggle, such as whether there are scars and the specific parts of the injury.

Third, efforts must be made to dispel the ideological concerns of insiders. The testimony of insiders is an important piece of evidence, which plays an important role in determining the facts of the case and the facts of the crime. Some insiders have serious concerns and are afraid of retaliation; some insiders may have some relationship with the case and are afraid of being implicated, and may be afraid or unwilling to testify. To this end, case investigators must patiently and meticulously do a good job in the ideological work of insiders. The first is to establish feelings and move people with emotion. We need to care about those who are in the know, understand their inner difficulties, sympathize with their situation, and care about the difficulties they face. At the same time, we should do our best to help solve some practical difficulties, and through these practical actions, we can impress them, influence them, and let them take the initiative to provide testimony. The second is to remove obstacles and eliminate concerns. Carry out targeted persuasion education based on the specific ideological concerns of the insiders, move them emotionally and understand them with reason, and encourage them to provide the true situation of the case. The third is to protect insiders and enhance their confidence in testifying. When looking for insiders to collect evidence, it is best to wear plain clothes, make some excuses, and try not to attract other people's attention. When possible, choose the location of the inquiry to avoid people's sight and reduce their mental burden. The fourth is to pay attention to inquiry methods and pay attention to strategies. You cannot scare the insiders with your identity, and you cannot use big words to suppress the insiders to reduce the resentment of the insiders.