Chapter 154 Footprints

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

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

Jiang Yuan sprayed a row of fixatives in the stairwell. After the ones behind were all sprayed, the footprints in front gradually appeared.

At this time, ordinary on-site inspections or trace inspections usually sprinkle powder for development. Jiang Yuan did not need this step, so he looked at the footprints and savored the original flavor.

But he only took a rough look.

Most of the footprints should be left by the security guards.

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

Jiang Yuan continued to spray the fixative and put the transparent inspection foot pedals in the position without footprints, and moved forward step by step until all the stairs from the 27th to the 29th floor were sprayed.

Then, Jiang Yuan put on the specially transported on-site inspection footprint light source.

"On-site inspection footprint light source" sounds like a very professional equipment, but it is actually a high-power LED lamp. The shell is configured to give it a relatively reasonable height and rotation angle.

Of course, lithium batteries are indispensable, which can not only ensure the portability and power requirements when used outdoors, but also ensure the price and profit.

The footprint light source purchased by Ningtai County has a power of 100w and a color temperature of 6000k, which can basically simulate natural daylight. Hitting the ground, the footprints that have just been sprayed with a fixative immediately give people a sense of being clearly visible.

Finding footprints, fingerprints, and trace evidence actually use the same kind of things.

The thing is really good and convenient, but before that, Jiang Yuan was too lazy to bring it over.

Like today at the take-off and crash site, which is more than ten meters away, Jiang Yuan used natural light during the day and a small portable light source at night, and found a lot of trace evidence. It doesn't seem to need such a large light source.

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

Ordinary murders, or murders that normal police can encounter, are basically junior criminals, veterans who have committed crimes many times, and most police officers will never encounter them in their lifetime.

However, if there is really a criminal who "returns to the crime scene", he must not be faced as a junior player.

Anyone who can do this can probably be described as calm and unhurried.

And the calmness at the crime scene often means that there are few traces.

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

Wang Zhong, who came with him, watched Jiang Yuan move the light source twice, and immediately ran over and took the initiative to take over the task of moving the light source.

Jiang Yuan then thanked him, then stood on a transparent footrest, holding his waist, resting while observing the many footprints in front of him.

Compared with "calm and unhurried", how could the police lose to criminals.

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

Things like technological leadership are rarely possessed by police.

Most of the time, the police are "calm and unhurried", which means slow work and iron feet, organization and execution.

Jiang Yuan restrained his desire to make a quick judgment and looked at the footprints one by one.

The security guards had the most footprints, but they were also the lowest priority.

Some of the security guards' footprints were still on the footprints in front, which showed that this was the direction of the patrol.

Jiang Yuan was also glad that he notified the captain at this time, otherwise, if he came by himself, the security guards would not only trample the scene in advance, but it would also be difficult to organize the security guards to patrol in the future.

If the murderer was the security guard...

Jiang Yuan shook his head and still focused on the footprints other than the security guards' leather shoes.

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

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

The deep footprints were from bottom to top, wandering around on the spot for several footprints, and then walked out from inside to outside...

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

Generally, cases are actually collected by ordinary criminal police or criminal police in cooperation with on-site investigation. In other words, collecting footprints and fingerprints are both basic skills of criminal police.

In addition, at the scene of general cases, criminal police also selectively collect fingerprints and footprints, otherwise, if all fingerprints and footprints in the room are collected, few technicians can afford it.

That is to say, the murder scene can be so luxurious.

As for now, facing this line of fresh footprints under the feet, everyone can see the problem.

This is the most likely footprint of the murderer that we have seen so far.

The direction of the footprints is also very telling.

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.

If we go to the fire staircase on the 27th floor, we can find that this person came in from the fire door on the 27th floor.

He ran to the 28th floor. If he wasn't the murderer, it would be a coincidence.

"Door handle." Wang Zhong reminded Jiang Yuan in a low voice, asking him to look for fingerprints first.

Jiang Yuan nodded. There were multiple footprints on the ground, and it would be in time to pick them up later.

Jiang Yuan stepped on the footsteps and came to the fire door. He turned on the light and looked at the door handle first.

At first glance, it was a clean stainless steel door handle, the kind that was very reflective.

"Wipe it." Jiang Yuan whispered.

Wang Zhong was stunned: "So careful?"

Jiang Yuan nodded.

Although he wanted to find evidence, he had to admit that it was becoming increasingly difficult to find fingerprint evidence.

The more careful the perpetrators were, the more they would avoid leaving fingerprints. The simplest method was to wear gloves, some would wipe the places they had touched, and some would burn their fingers directly.

Wang Zhong looked a little disappointed, but Jiang Yuan could still accept it.

He looked at the footprints on the ground, a little dazed.

If he was the only one present at the time, and this guy came out again, wearing gloves on his hands, lowering the brim of his hat, and wearing a mask...

"Can the footprints reveal age and height?" Huang Qiangmin shouted from the periphery.

Jiang Yuan quickly put his mind back, took another look at the footprints, and said, "Male, aged 45 to 49, of medium build, about 170 cm tall..."

It was just like an ordinary person.

This was also the most troublesome part of footprint identification, as it could reveal too little specificity.

Huang Qiangmin followed Jiang Yuan's instructions and sent a group message. Seeing that the people around him were in a bad mood, he encouraged them, "There shouldn't be many people aged 45 to 49 in this building. Let's look for them first."

Jiang Yuan nodded slightly. Dust footprints still don't provide as much information as blood footprints. But anyway, this is a step closer.

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

"Is the age accurate? Do you want to expand it a little bit?" Wu Junhao had been standing in front of him and only spoke at this time.

"I'm talking about the age. If you are worried, expand it by two years." Jiang Yuan took into account the age habits in different regions and followed Wu Junhao's meaning and relaxed 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.

To be honest, the simplest way to judge age by footprints can be easily learned by ordinary people.

That is to divide the footprint into four equal parts vertically. The innermost first line area has an age range of 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 outermost fourth line area is 40 to 49 years old.

When Jiang Yuan made his judgment, he naturally had to combine other information, but doing half of it was enough.

"Multi-band." Jiang Yuan shouted again.

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

This thing is also used to assist in finding traces.

It is especially useful for finding trace evidence.

Many objects will emit fluorescence at the right band.

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.

However, there were none.