1. Footprint inspection is a branch of criminal technology, a trace in trace material evidence inspection, and one of the four most common trace "hands and feet guns" in handling cases. Footprint inspection plays an important role in trace inspection system and plays a vital role in solving crimes. Footprint inspection does not have the huge database support function of fingerprint DNA, but it does not affect its great role in investigation. On the one hand, footprint inspection can provide the same identification basis. For example, if there are shoe prints on the scene, we can determine whether the footprints on the scene are left by the same pair of shoes by comparing them with the sample footprints. If there are red footprints or sock prints at the scene, we can compare them with the red footprints or sock prints of the samples, so as to determine whether the two footprints or sock prints are left by the same person; On the other hand, footprint inspection can also provide some very effective analysis conclusions for criminal investigation, such as analyzing the number of perpetrators and providing the characteristics of the perpetrators such as age, height and occupation. In addition, the conclusion of footprint identification is also one of the important evidences in litigation.

Five remarkable characteristics

Compared with fingerprints, bullet marks, tool marks or DNA identification, footprint inspection has very remarkable characteristics.

First, the appearance rate of footprints in the scene is very high, and the extraction rate is also very high. Fingerprint identification or DNA identification is a very mature personal identification technology, but due to the limited remaining conditions, the extraction rate is often not high in field investigation. Generally, the probability of obtaining fingerprints in field investigation is only about 14% in China, and the extraction rate of DNA is much lower than that of fingerprints. Compared with fingerprint marks or DNA extraction rate, the probability of footprints is much higher. No matter whether the suspect wears gloves or not, no matter whether the crime time is relatively short, he will leave a corresponding footprint.

Second, footprints are more difficult to disguise than other traces. Even if the suspect does not wear gloves when committing a crime, he will pay special attention to many actions in order to avoid leaving fingerprints. However, as long as the suspect commits a crime, he will inevitably walk on the scene. As long as he walks, he will show normal walking characteristics. Therefore, compared with other traces, footprints are more difficult to disguise.

Thirdly, footprint inspection is the most effective means of on-site analysis. An important task of on-site investigation is to determine the investigation direction from a technical point of view, accurately judge the nature of the case, judge the on-site route, and judge the crime process and the number of people. Because of the high occurrence rate of footprints in the scene, the most important basis for judging the basic elements of the scene from a technical point of view is footprints, such as analyzing and judging the number of criminals, and the most important technical basis is the type and number of footprints in the scene. The fingerprints left by the suspect at the scene cannot reflect the whole crime process, but every action of the suspect at the scene will leave a corresponding footprint. As long as there are no mistakes in the footprint extraction process, the whole crime process will be found more complete. Therefore, the discovery, extraction and inspection of footprints is one of the most effective means of on-site analysis.

Fourth, it can reflect many personal characteristics of criminal suspects. We can judge the age, height, posture, occupation and other characteristics of the wearer through the preliminary test of footprint size and pressure, and provide more clues for investigation and solving crimes.

Fifth, footprint inspection, like fingerprints and DNA, can not only identify the same thing, but also identify people. Including the identification of shoes and the identification of red footprints or socks.

Traces left by criminals when committing crimes, such as fingerprints, footprints, smells, etc. These marks can not only reflect some physiological characteristics of the perpetrator, but also reflect some psychological state at that time. For example, criminals usually leave footprints on the scene when they enter and leave the scene. According to the characteristics of the extracted footprints, we can often make such an analysis: those who are light and slow and have clear gait are the first to enter the crime scene and eavesdrop on whether there is any movement around them while walking; Those who strode hard were excited when they fled the scene, either because of the success of the crime or because of fear; Most people with gait disorders hallucinate out of fear or intention.

2. The method of inferring height by footprint, and the method of estimating and judging height by using the proportional relationship and internal relationship between footprint and stride length and human height. The difference in height depends on the length of legs and the length of trunk. Long legs take a big step, short legs take a small step. In ancient China, there was a saying that there were "seven seats, five plates and six tables", and the height was enough. Everyone's foot length and body length have a certain proportional relationship. Therefore, the total body height in feet is generally 7 units, that is, the ratio of height to foot length is 7: 1. According to this law, according to the specific situation of footprints, through concrete analysis and using certain coefficients, we can calculate the approximate high birth number. Approximate methods of footprint calculation include: approximate height method of single barefoot footprint calculation; Height push algorithm of single shoe footprint; Simple estimation method of on-site sole height: the method of estimating height according to footprints.

A, the calculation method of the height of a single barefoot footprint

The method of estimating height by single barefoot footprint refers to the method of estimating personal height by using single, plane, three-dimensional and local barefoot footprint.

(1) barefoot footprint. Mainly measure the total length of the barefoot plane footprint left at the scene, and then calculate the height according to the following formula. Total length of barefoot plane footprint (cm) × 7 = height (approximate)

(2) Barefoot stereo footprint. Not only on the sole of the foot, but also on the back of the heel and toe tip may leave traces. In this way, the total length of footprints is slightly larger than the actual length of barefoot, so after using the above formula to get the approximate figure, it is necessary to add or subtract about 3 cm according to the specific situation.

(3) For the partial footprint of barefoot, please refer to the following proportions: the ratio of barefoot board to height is 65,438+0: 8, the ratio of toe width to height is 65,438+0: 65,438+07, the ratio of barefoot sole width to height is 65,438+0: 25, and the distance from arch to heel center is× 25. In practice, the reference coefficient of birth height can be calculated by using these proportional analysis.

Second, the method of calculating the height of a single shoe print

The method of estimating height by single shoe print refers to the method of estimating barefoot length by using shoes or footprints on the spot, and then calculating birth height according to barefoot length. The specific method is: firstly, measure the full length of the on-site shoe trace, then reasonably subtract the front and rear edges of the sole, as well as the difference between the inside and outside, the margin and the main trace are larger than the molded body, and then calculate the approximate number of birth height with the newly obtained approximate length of the barefoot plane trace ×7. To calculate the height by this method, we must first understand the relationship between the sizes of various machine-made shoes and the national unified shoe size. The national unified shoe size, also known as the "four shoes" unified shoe size, has the following characteristics: 1. The unified shoe size is determined according to the length of the foot (cm), 1 cm is a shoe size, and 0.5 cm is a half shoe size. When wearing shoes, in order to make the feet still have room for various movements, the length inside the feet must be greater than the length of the feet, that is, there must be "allowance". The "allowance" standard for all kinds of shoes is: plastic sandals for men and women are 0.5cm, third plastic sandals 1 cm, rubber shoes 1 cm, women's leather shoes1.2cm, men's leather shoes1.5cm and men's and women's cloth shoes are 0.8cm.. Therefore, the actual length of shoes should be the length of each shoe plus the standard "allowance" of various shoes. The conversion method of shoe size and sole length is: sole length = shoe size+internal and external difference+allowance. The so-called inside-outside difference refers to the difference between the inside length of the shoe and the outside length of the sole, that is, the actual length of the shoe plus the thickness of the front and rear uppers, so as to calculate the length of the sole. The difference between different types of shoes inside and outside is different. In most cases, the traces of rubber and plastic soles are about 0.5- 1.5 cm larger than the specified shoe size. Cloth shoes with rough patterns and edges are about 1.5-3 cm larger than the specified shoe size. Leather shoes logo: the flat bottom is about 1- 1.5 cm larger than the specified shoe size. The heel of the nail is about 1-2 cm larger than the specified shoe size. The above general differences can be used as parameters to calculate the shoe size and height according to various shoe tracks on site. The main application is based on the specific production technology of various shoes in various places, investigation and research, accumulation of information and comprehensive analysis, in order to accurately reduce the actual internal and external differences. Second, the unified shoe size type: width (fat) As far as the country is concerned, adults are divided into five types, which are respectively represented by (1), (2), (3), (4) and (5), of which (1) is the widest and (5) is the fattest. The difference between each type is 0.7 cm, and five types can be added according to the needs of each region, that is, 3.5 cm. The extreme values of fat type and thin type are determined by measuring toe circumference and statistical processing of data.

3. Footprint test is basically used in general criminal cases.