Wang Xuming: Physical evidence appraisal mainly includes documents, traces and trace identification, but is not limited to these

We usually talk about physical evidence identification, including document identification, trace identification and trace identification. But by no means limited to that. Let's take a look at each of them:

I. Document Appraisal:

"Document appraisal" refers to the use of the principles and techniques of document inspection to identify the handwriting, seals, seals, seals, production and tools of documents, and the formation time of documents.

Documents refer to official documents and letters, but the documents used as evidence in actual case handling often exceed the scope of official documents and letters, such as tickets, ferry tickets, air tickets, invoices, receipts, renminbi, etc., and the authenticity of their contents and production methods need to be identified.

Document appraisal is the analysis, identification, and identification of related issues such as writing, text production, the specific content reflected in the physical evidence of the document, the method of making the document, and the authenticity of the document involved in the case. Document appraisal can not only provide evidence in analyzing the case facts, narrowing the scope of the investigation, clarifying the direction of the investigation of the case, and identifying criminal suspects.

Document appraisal includes handwriting appraisal, forged and altered document appraisal, printing, copying and printing appraisal, appraisal of material material materials of documents, and appraisal of document production time.

Handwriting is a kind of writing symbol that the writer uses a pen or other writing instrument to write on paper or other materials to reflect the characteristics of the writing habits of the writer. Due to the different physiological characteristics, psychological factors and ways, methods, environments, and conditions of learning to write, the writing habits determined by these factors are also different.

The main purpose of handwriting identification is to determine whether the handwriting left on the physical evidence of the document is left by a person, and to confirm whether the handwriting left in different places was written by a single person. Forgery or alteration of documents refers to the forgery of real documents designed and manufactured according to a certain real sample, or according to the special needs of individuals, using various technical methods, or by means of digging, scraping, rewriting, filling, fading, altering, splicing, etc.

In forensic appraisals, forged documents often encountered include forged passports, identity cards, negotiable securities, renminbi, foreign currency, letters of introduction, bills, etc. The identification of documents is mainly carried out through the comparative inspection of the test material and the authenticity, to compare the production of the layout, but also from the layout content such as patterns, text, printing, shading, printing ink, paper and anti-counterfeiting materials to identify.

In order to better observe and compare some of the small features in the document, inspectors need to identify them with the help of a microscope, a comparison projector, a UV lamp, or other specialized identification instrument. After a suspicious document has been determined to be forged, it is sometimes necessary to further determine the specific method of forgery to provide direction for investigation and provide clues for the arrest of criminal suspects.

With the development of office modernization, computers, printers, copiers, etc. have been widely used in people's daily study, work and life. At present, in the process of investigating the case, the identification of printers and copiers for the production of documents has begun. In the investigation of cases, the appraisal of documents and materials is of great significance to determining the direction of investigation, narrowing the scope of investigation, and investigating criminal suspects. The material materials of the documents refer to the paper, ink, ink, printing oil and other materials used in the preparation of the documents.

Second, trace identification:

"Trace identification" refers to the use of trace science principles and techniques to identify issues related to the identity of traces formed by the human body and objects, and the correlation between separated traces and the original whole. Using the theories and techniques of firearms, ammunition science and ballistics, the guns and the residues after shooting, the traces of residue formation, homemade firearms and ammunition and lethality are identified.

Traces refer to material changes such as the movement of objects formed on material objects, the addition or decrease of matter, and changes in morphological structure formed on material objects due to the movement of people, animals or other objects. Trace identification is still widely used in various litigation activities, and almost all scenes will involve the identification of traces.

In litigation activities, the most common trace identification mainly includes fingerprint identification, footprint identification, tool trace identification and bullet trace identification. Fingerprint refers to the pattern of the papillary line on the finger. Fingerprints have the characteristics of different people, traces of touch, arrangement and lifelong unchanged. Because the fingerprint is covered with sweat glands and constantly secretes sweat, often from other objects stained with grease, paint, dust, blood, etc., when it touches the object, it will inevitably leave a fingerprint, and the stability of the fingerprint is very prominent, once formed, it will not change for life. Fingerprints are known as the "king of evidence" in litigation, and individuals who have left fingerprints can be directly identified through fingerprint identification. In recent years, although some perpetrators have increased their awareness of anti-investigation, with the development and application of high-tech instruments such as computers and lasers, the technology of fingerprint discovery, display, extraction and comparison has also made leaps and bounds, which has greatly improved the evidentiary role of fingerprints in judicial activities. In criminal proceedings, through the analysis and identification of fingerprints, it is possible to provide direction and evidence for the analysis of the case, for the parallel case, and for the identification of criminal suspects.

Footprints are the image traces of the soles of feet, shoes, socks, etc. formed by people's contact with the ground or other ground when standing and walking. Footprints are an important physical evidence often used in criminal investigations. Footprints have two major types of characteristics: one is the image characteristics of the footprints, that is, the appearance of barefoot, shoes or socks reflected in a single footprint; the other is the pace characteristics of the footprints, that is, single or trip footprints, reflecting the characteristics of people's walking habits, these characteristics are formed and fixed after long-term practice and repeated practice, due to gender, age, height, weight, occupation, walking posture and other factors, each person reflects the pace characteristics are also different. Through the analysis and identification of footprints, it is possible to judge the height, age, weight, walking posture, etc. of the person, and also analyze the time left behind, the direction of the perpetrator's escape, etc. When the conditions are better, follow the footprints, or use the footprints as a source of police dogs to directly capture or identify the criminal suspects.

Tool marks refer to the traces formed on an object or human body when using a tool to destroy an object or hit a human body. Tool marks are one of the most common marks on crime scenes, and the perpetrator uses a cone, pliers to pry the door to press the lock, and cut the obstacle to leave the tool trace. Through the analysis and appraisal of the traces of the tools, the means of committing the crime can be determined, the characteristics of the perpetrator's personal behavior can be analyzed, the nature of the case can be determined, and evidence can be provided for the establishment of the direction of investigation.

Bullet marks are traces formed by the gun during the firing of bullets. It includes marks left on the warhead, shell casing, and traces accompanying the shot. When a bullet is fired, it usually goes through three processes: reloading, shooting and shelling. Under the strong pressure generated by mechanical action and ammunition combustion, the warhead, shell and gun parts will produce strong friction, thus forming image marks reflecting the inner wall of the barrel, magazine mouth, firing pin and other image marks on the bullet head and shell. When the bullet is fired, along with the bullet penetrating the target, trace substances such as gun oil, unburned gunpowder, and soot scale spewed from the barrel will often be attached to the inside of the shell wall and the surface of the warhead of the target, and these trace substances will form traces. Through the analysis of the bullet traces, it is possible to judge the type of gun fired and determine the launch of the gun; it is also possible to judge the shooting distance, shooting angle, and shooting order of the perpetrator, determine the nature of the case, and provide direction for investigation.

Third, trace identification:

"Trace identification" refers to the use of physics, chemistry and instrumental analysis methods to identify the type of material, the homogeneity and identity of the specimen and the suspect sample through qualitative and quantitative analysis of the composition and structure of the relevant materials. At the scene or other places related to the case, various small amounts of small and micro substances extracted may become trace physical evidence.

In today's criminal crimes, the perpetrator's means and methods of committing crimes are becoming more and more cunning, carefully planned in advance, disguised everywhere in the event, and destroyed after the fact, it is difficult to extract obvious traces of physical evidence at the crime scene, because the trace physical evidence has a small amount of small size, it is easy to leave at the scene, but it is not easy to be noticed, often so that the perpetrator can not destroy or disguise. With the rapid development of site investigation technology and trace evidence analysis technology, the scope and role of trace evidence are constantly expanding. In judicial practice, the common identification of trace physical evidence includes the identification of explosive residues, shooting residues, arson physical evidence, dirt, dust, dust, glass or metal residues, as well as the identification of fibers, textiles, plastics, rubber, grease, paint and other physical evidence.

With the development of science and technology, the ability and scope of human beings to use nature, manufacture and use tools are becoming more and more extensive, and the threats facing mankind will also increase, and in the face of many uncertainties, the most critical evidence for fighting crime and proving crime is physical evidence. Therefore, the identification of research evidence will continue to encounter challenges, such as the "clues" left in the Internet data transmission, which will become a new "physical evidence identification" in the future.