civil forensic

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 to dry and fix.

Jiang Yuan sprayed a row of fixative in the stairwell, and after spraying all the back ones, the front footprints gradually appeared.

At this time, for ordinary spot inspection or trace inspection, powder is usually sprinkled for development.Jiang Yuan didn't need this step, so he just looked at the footprints and tasted the original taste.

But it's just a quick look.

Most of the footprints should have been left by the security guards.

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

Jiang Yuan continued to spray the fixative, and put the transparent scouting step on a position where there were no footprints, and pushed forward step by step until all the stairs on the 27th to 29th floors were sprayed.

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

The "Site Survey Footprint Light" sounds like a very professional device, but it is actually a high-power LED light.The housing is configured to have a relatively reasonable height and rotation angle.

Of course, lithium batteries are essential, which can not only guarantee the portability and power requirements when used outside, but also guarantee 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 sunlight.Hitting the ground, the footprints that have just been sprayed with fixative immediately give people a feeling of fine detail.

Looking for footprints, looking for fingerprints, looking for trace physical evidence, they all use the same kind of things.

The things are really good and convenient, but before that, Jiang Yuan didn't bother to bring them over.

For example, at the scene of the crash today, which is more than ten meters away, Jiang Yuan used natural light during the day and a small portable light source at night to find a lot of trace evidence, and it felt like 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 of course you have to use what equipment you have.

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

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

Anyone who has achieved this step can probably be described as calm and unhurried.

The calmness of the murder scene often means that there are few traces.

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

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

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

How can the police lose to criminals than "take it easy".

When it comes to technology, the policing system has never won.

Such things as technological leadership are rarely possessed by the police.

Most of the time, what the police have is "calm and unhurried", that is, hard 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.

Security guards have the most footprints, but also the lowest priority.

The footprints of some security guards still follow the footprints in front of them. It can be seen that this is the direction of the patrol.

Jiang Yuan was also fortunate to have notified the team leader at this time, otherwise, if he came by himself, the security guards would have trampled on the scene ahead of time, and it would be difficult to organize the security guards to patrol in the future.

If the murderer is a security guard...

Jiang Yuan shook his head, but first set his sights on the footprints other than the security leather shoes.

There are three sets of footprints here, two of the lighter ones and one of the darker ones.

The age of the two sets of pale tracks is about 30 years old, which happens to be a top-down walking track.

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

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

Ordinary cases are actually investigated by ordinary criminal police or criminal police in cooperation with the scene. That is to say, taking footprints and fingerprints is the same as taking fingerprints, which are the basic skills of criminal police.

Moreover, at the scene of a general case, the criminal police also selectively take fingerprints and footprints. Otherwise, they take all the fingerprints and footprints in the room, and few technicians can afford it.

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

As for now, facing the new footprints under their feet, everyone can see the problem.

This is what I have seen so far, most likely the footprints of the murderer.

The direction of the footprints can also explain the problem.

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.

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

Just ran to the 28th floor. If it wasn't for the murderer, it would be too coincidental.

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

Jiang Yuan nodded.There are multiple footprints on the ground, and it will be too late to get them later.

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

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

"It's been wiped." Jiang Yuan said in a low voice.

Wang Zhong was taken aback: "So careful?"

Jiang Yuan nodded.

Although I really want to find evidence, I have to say that it is getting more and more difficult to find fingerprint evidence now.

Thoughtful perpetrators will take various measures to avoid leaving fingerprints.The simplest is to wear gloves, and sometimes it is time to wipe the touched position, and some 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 and was a little dazed.

At that time, if he was the only one present, this guy came out again, put on gloves on his hands, lowered the brim of his hat, and put on a mask...

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

Jiang Yuan quickly put his heart away, looked at the footprints again, and said: "Male, aged 45 to 49 years old, of medium build, about 170 tall..."

Just like an ordinary person.

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

According to what Jiang Yuan said, Huang Qiangmin first sent a group text message, and then saw that the people around him were in a bad mood, and encouraged him: "There should not be many people between the ages of 45 and 49 in this building. Look for it first."

Jiang Yuan nodded lightly.Dust footprints are still not as informative as blood footprints.But anyway, it's a step closer.

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

"Is the age accurate? Do you want to expand it a little more?" Wu Junhao had been standing in front of him, and only then did he speak.

"I'm talking about one year old. If you're worried, let's increase the age by two years." Considering the age habits in different regions, Jiang Yuan followed Wu Junhao's intention and relaxed the two-year-old age.

However, as far as the accuracy of judgment is concerned, judging age through footprints is indeed not as accurate as judging height and weight.

Speaking of which, the simplest way to judge age through footprints can be easily learned by ordinary people.

It is to divide the footprints into quarters vertically, the innermost first line area, the age range is 18 to 23 years old, the second line area is 24 to 29 years old, the center line is 30 years old, and the third line area is 31 to 39 years old. The outermost fourth tier is 40 to 49 years old.

When Jiang Yuan made a judgment, he naturally had to combine other information, but it was almost half done.

"Multiple bands." Jiang Yuan shouted again.

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

This thing is also to help find traces.

It is especially useful for finding trace evidence.

There are many items that emit fluorescence under the appropriate wavelength band.

Jiang Yuan adjusted the multi-band light source to 450nm light and began to search near the fire doors.

There may be fibers left behind.

However, it did not.

(End of this chapter)