Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

Chapter 260 Technical Analysis

From a professional point of view, footprint identification analysis mainly focuses on three elements.

Sculpture bodies, which are the subject of footprints, bare feet, shod feet or socked feet.

The bearing body is the ground or other objects bearing footprints.

The third important factor is the force. In addition to the gravity of the human body, there is also the muscle contraction force of the soles of the feet.

In the vast majority of cases, the type of footprints encountered are shoe prints.

It is rare for a suspect to walk around a crime scene without shoes, barefoot or in socks.

The footprints identified by Lu Chuan are also shoe prints.

This type of footprint, compared with barefoot prints and sock footprints, has a distinctive feature that the shape of the shoe print is strictly limited by the shape of the shoe.

For example, a size 41 foot can also wear a size 42 shoe, and even a size 43 or even a size [-] shoe.

This brings a lot of uncertainty to the footprint identification analysis.

Therefore, the size and length of footprints are confusing in the analysis of footprint identification.

In general surveys, based on the fixed formula of foot length and height, there will inevitably be errors.

Although Lu Chuan has not been to the scene to see the footprints, nor has he seen the footprint model, but just from the photos, he knows that the current survey by the Criminal Police Brigade of the High-speed Railway New Area should be problematic in judging the height of the suspect. .

Lu Chuan first analyzed the measurement data of shoe prints.

The comparison of the total length of the foot, the width of the arch, the width of the sole, and the width of the heel can roughly obtain the height and weight of the owner of the footprint.

But it's only a range.

It depends on the depth of the footprints on the ground.

This requires experiments to verify, comparing the weight of the owner of the shoe print.

This is actually the easiest.

People of different weights leave footprints of different depths on the same ground.

Just find a person with a known weight, step on another footprint at the place where the suspect left the shoe print, and calculate the suspect's weight based on the comparison of the depth of the two footprints.

Of course, now that Lu Chuan only saw the photos, he couldn't make these measurements.

Only the basic situation can be analyzed.

During the current survey of the Criminal Police Brigade of the High-speed Railway New District, twelve groups of footprints were collected at the scene.

There are so many footprints, and among them are the footprints left by the suspect during his continuous march.

In this way, Lu Chuan can analyze the characteristics of footwork.

The first is the stride feature.

It can judge the suspect's walking step length, step angle and step width.

But generally speaking, determining the stride characteristics cannot be accomplished by one or two footprints alone.

Continuous, at least four or more forward footprints are required to analyze this aspect.

With continuous footprints, it is relatively easy to measure.

"Step length... 45 centimeters."

Generally speaking, for adult males with a height of 1.7 meters to 1.8 meters, the stride length is usually between [-] centimeters and [-] centimeters.

Of course, there are still requirements for the current survey measurement step.

The distance from the toe of the back foot to the heel of the front foot, not including the length of the feet, is the stride length.

However, the suspect's stride length was only 45 centimeters.

This data can be said to be significantly lower than the average step length of adult males.

There are three standards for judging the step length in surveys. Generally speaking, it is a long step if it exceeds 71 centimeters, and it is called a medium step if it is [-] to [-] centimeters.

Anything below [-] centimeters is a short step.

The suspect's stride length is the shortest of short steps.

However, combined with Lu Chuan's inference on the suspect's height just now, it is also reasonable.

"Step angle...outward 7.2 degrees"

Most people's gait angles are around 6 degrees, close to 7 degrees, and the suspect has a slight horoscope.

"Step width... 8.1 cm, normal."

The measurement and analysis of step width is actually more complicated than step length and step angle.

Everyone's step length and step angle are not unique.

It is very easy to find two people with the same step length.

The same is true for the step angle. For the vast majority of people who walk normally, the step angle is basically around 6.7 degrees.

Even if it is a little close, it will not be particularly large.

But the step width is different.

In reality, it is rare to find people with exactly the same stride width.

The current survey divides the step width into many categories.

Such as separate steps, parallel steps, step-by-step, straight-line steps, staggered steps and so on.

The suspect's stride width is within the range of most normal people.

The last thing Lu Chuan did was analyze the suspect's gait characteristics.

The gait characteristics of different people have different characteristics.

For example, when some people walk, their heels touch the ground first, while others touch the ground with their soles first.

This is the footing feature.

There are also characteristics of kicking. Some people use their soles of their feet to lift their feet, some use their heels, and some use their toes.

In this case, in fact, every footprint is a dynamic.

According to the different pressure changes in the front, middle and back of the footprints, the characteristic information of many suspects' walking can be judged.

For example, the kick mark at the start is reflected in the footprints that the forefoot marks are deep. If it is on the dirt ground, the soil will move backward.

Another example is the digging mark at the start, the toe is pressed down, showing a crescent-shaped depression.

Lu Chuan's identification and analysis was very careful, more than an hour passed, and it was not yet completed.

Liu Guodong and others did not bother.

Like identifying and analyzing fingerprints, this kind of work needs to calm down and concentrate on doing it.

Of course, compared with the identification and analysis of fingerprints, the identification of footprints requires a lot of fine measurement work and data calculation work.

Based on Lu Chuan's work experience, doing footprint identification and analysis is more tiring than doing fingerprint identification and analysis.

"call……"

Two and a half hours later, when it was almost time to get off work, Lu Chuan finally let out a long breath.

"nailed it?"

Lao Bai brought over a cup of tea, Lu Chuan took it, and gulped it down.

"It's almost there, but I still have to go to the scene to see, or some data is not sure."

Lu Chuan looked at Liu Guodong.

The other party nodded: "I just called to ask, and the scene is still there, so I should go and have a look."

"Are you going now?"

Lao Bai looked at the sky, and it would be dark in a while.

"Go, long night and dreamy."

"Okay, I'll go with you, Lao Yang wants to go home to accompany his son, I have nothing to do."

"Master, let's go then."

"Okay, I'll contact the high-speed rail new area, and Zhang Qi will send someone to cooperate with you."

after an hour.

Baomi field at the west end of Xinjian Village, High-speed Railway New Area.

In Haizhou at the end of April, the corn seedlings had just grown, not as high as chopsticks.

But the greenery is lush and the air is fresh.

"Mr. Lu, this is the scene of the crime."

The person who came from the high-speed rail new area was the current surveyor who collected the footprints, Sun Miao.

The two knew each other, and at the beginning of the year, they participated in the fingerprint competition of the Municipal Bureau together.

However, Sun Miao used to call Lu Chuan Lu Chuan, but now he is Teacher Lu.

(End of this chapter)