Chapter 155: Footprints

The dust fixative purchased by the Ningtai County Bureau is made of alcohol solvent with rosin.

This is a very old-fashioned fixative, with slightly poor transparency and a long time for drying and fixing.

Jiang Yuan sprayed a row of fixatives in the stairwell. The later ones were sprayed, and the earlier footprints gradually appeared.

At this time, ordinary crime scene investigation or trace inspection usually sprinkles powder to develop the image. Jiang Yuan doesn't need this step, just taste the original flavor after looking at the footprints.

But it's just a rough look.

Most of the footprints should be left by security guards.

Wanghe Building's security guards all wear leather shoes and small ties, which are useless, but they look quite formal.

Jiang Yuan continued to spray the fixative and placed the transparent investigation foot pedals in positions without footprints, advancing step by step until the stairs from the 27th to the 29th floor were all sprayed.

Then, Jiang Yuan placed the specially transported crime scene investigation footprint light source.

"Crime scene investigation footprint light source" sounds like a very professional piece of equipment, but it is actually a high-power LED light. It is configured with a shell, making it have a relatively reasonable height and rotation angle.

Of course, lithium batteries are indispensable, which can guarantee the portability and power requirements when used outside, and can also guarantee the price and profit.

The power of the footprint light source purchased by Ningtai County is 100W, color temperature 6000K, which can basically simulate natural daylight. Shining on the ground, the footprints that have just been sprayed with fixative suddenly give people a feeling of being visible in every detail.

Finding footprints, finding fingerprints, and finding trace evidence are actually all the same kind of things.

Things are indeed very good and convenient, but before this, Jiang Yuan was too lazy to bring them over.

Like today at the fall scene, which is more than ten meters away, Jiang Yuan used natural light during the day and a portable small light source at night, and found a lot of trace evidence, feeling that he didn't need such a large light source.

However, in the current situation, if you really encounter a criminal who "returns to the crime scene," then naturally you use whatever equipment you have.

Ordinary homicides, or homicides that normal police can encounter, are basically primary criminals. Most police officers will not encounter a veteran who commits crimes multiple times in their entire life.

But if there is really a criminal who "returns to the crime scene," then you definitely cannot face it as a primary player.

Anyone who reaches this step can basically be described as calm and composed.

And the calmness at the crime scene often means few traces.

The irradiation surface of the footprint light source is about 1 meter wide, but the depth is very large, so Jiang Yuan swept over piece by piece.

Wang Zhong, who came with him, saw Jiang Yuan move the light source twice, and immediately ran over, taking the task of moving the light source.

Jiang Yuan thanked him, stood on a transparent foot pedal, held his waist, and observed the many footprints in front of him while resting.

As for "calm and composed," how could the police lose to the criminal?

In terms of technology, the police system has never won.

Police officers rarely possess technological leadership.

Most of the time, what the police have is "calm and composed," is the water-grinding work and iron feet, is organization and execution.

Jiang Yuan restrained his desire to make judgments quickly and just looked at the footprints one by one.

Security guards' footprints are the most, but their priority is also the lowest.

Some security guards' footprints are still stepping on the footprints in front, which can be seen as the direction of patrol.

Jiang Yuan was also glad that he notified the brigade captain at this time. Otherwise, if he came by himself, the security guards would have stepped on the scene in advance, and it would be difficult to organize the patrol back and forth later.

If the murderer is a security guard...

Jiang Yuan shook his head, still putting the target on footprints other than security leather shoes first.

There are three sets of footprints here, two sets of footprints are relatively light, and one set of footprints is relatively deep.

The age of the two sets of light footprints is about 30 years old, which is exactly a walking track from top to bottom.

The deep footprint is from bottom to top, wandering for several footprints on the spot, and then walking out from inside to outside...

In fact, not only Jiang Yuan, but several people present noticed this line of footprints that looked new.

Ordinary cases are actually taken by ordinary criminal police or criminal police cooperating with crime scene investigation, that is to say, taking footprints and fingerprints are both basic skills of criminal police.

Moreover, at ordinary crime scenes, criminal police also have a choice to take fingerprints and footprints, that is to say, taking all the fingerprints and footprints in the room is something no technician can bear.

That is to say, homicide scenes can be so luxurious.

As for now, facing the line of new footprints under his feet, everyone saw the problem.

This is the footprint that is most likely to be the murderer seen so far.

The direction of the footprints can also explain the problem very well.

This person walked in from the 27th floor, stayed on the 28th floor for a while, and then pushed open the fire door on the 28th floor and walked out.

Go to the fire stairs on the 27th floor to see, and you can find that this person came in from the fire door on the 27th floor.

Just aiming at the 28th floor, if it weren't the murderer, it would be too coincidental.

"Door handle." Wang Zhong reminded Jiang Yuan in a low voice, letting him find fingerprints first.

Jiang Yuan nodded. There are multiple footprints on the ground, and it's not too late to take them later.

Jiang Yuan stepped on the foot pedal to the fire door, turned on the light, and looked at the door handle first.

At a glance, it was a clean stainless steel door handle, the kind that reflects light.

"Wiped." Jiang Yuan said in a low voice.

Wang Zhong was stunned: "So careful?"

Jiang Yuan nodded.

Although he really wanted to find evidence, he had to admit that it was becoming more and more difficult to find fingerprint evidence now.

Those who are more meticulous in committing crimes will take various measures to avoid leaving fingerprints. The simplest is to wear gloves, some wipe the touched position, and some directly burn their fingers.

Wang Zhong looked disappointed, and Jiang Yuan could still accept it.

He looked at the footprints on the ground, slightly dazed.

If he were the only one present, and this guy walked out again, wearing gloves, with his hat brim pressed low, and wearing a mask...

"Can footprints tell age and height?" Huang Qiangmin stood on the periphery and shouted.

Jiang Yuan hurriedly collected his mind, looked at the footprints again, and said: "Male, age 45 to 49, medium build, height about 170..."

It's just the appearance of an ordinary person.

This is also the most troublesome part of footprint identification; the specificity it can see is too little.

Huang Qiangmin sent a text message according to what Jiang Yuan said, and seeing that the people around him were in low spirits, he encouraged: "People aged 45 to 49 shouldn't be many in this building. Let's look for them first."

Jiang Yuan nodded slightly. Dust footprints are still not as good as blood footprints in providing information. But in any case, this can be considered a step closer.

As Huang Qiangmin said, the age group of 45 to 49 has already narrowed down a large range.

"Is the age accurate? Do you want to expand it a bit?" Wu Jun had been standing nearby, and only then did he speak.

"What I said is the actual age. If you are worried, expand it by two years." Jiang Yuan considered the age habits of different regions and followed Wu Jun's meaning to relax it by two years.

However, in terms of the accuracy of judgment, judging age by footprints is indeed not as accurate as judging height and weight.

If you want to talk about it, the simplest way to judge age by footprints, ordinary people can easily learn.

That is to divide the footprint into four equal parts vertically. The first line area closest to the inside, the age range is 18 to 23 years old, the second line area is 24 to 29, the center line is 30 years old, the third line area is 31 to 39, and the fourth line area furthest to the outside is 40 to 49 years old.

When Jiang Yuan judges, he naturally has to combine other information, but doing it to half the degree is about the same.

"Multi-band." Jiang Yuan shouted again.

Immediately, a police officer ran out and brought a multi-band light source machine back.

This thing is also used to help find traces.

It is especially useful for finding trace evidence.

Many items will emit fluorescence under the appropriate wavelength.

Jiang Yuan adjusted the multi-band light source machine to 450 nanometers of light and began to search near the fire door.

Maybe there will be fibers left behind.

However, there were none. ===== CHAPTER 156 =====