The dust fixative purchased by the Ningtai County Bureau is made of alcohol solvent added with rosin.
This is a very old-fashioned fixative, with slightly poor transparency and a long drying and fixing time.
Jiang Yuan sprayed a row of fixatives on the stairwell. After all the sprays at the back were finished, the footprints in the front gradually appeared.
At this time, for ordinary spot inspection or trace inspection, powder is usually sprinkled for development. Jiang Yuan does not need this step, just look at the footprints and taste the original flavor.
But it's just a brief look.
Most of the footprints should have been left by security guards.
The security guards at Wanghe Building all wear leather shoes and small ties, which are useless, but they look quite formal.
Jiang Yuan continued to spray the fixative, placed the transparent surveying pedals where there were no footprints, and moved forward step by step until all the stairs from the 27th to 29th floors were sprayed.
Then, Jiang Yuan set up a specially brought light source for on-site inspection of the footprints.
The "on-site survey footprint light source" sounds like a very professional device, but it is actually a high-power LED light. It is equipped with a shell so that it has a relatively reasonable height and rotation angle.
Of course, lithium batteries are essential, not only to ensure portability and power requirements when used outside, but also to ensure 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. When it is hit on the ground, the footprints that have just been sprayed with fixative will immediately give people the feeling of being detailed.
Looking for footprints, fingerprints, and trace evidence all use the same kind of things.
The thing is indeed very good and convenient, but before that, Jiang Yuan was too lazy to bring it over.
For example, at the landing site today, which was about ten meters away, Jiang Yuan used natural light during the day and a portable small light source at night to find a lot of trace evidence. It seemed that there was no need for 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 in other words, the murders that normal police officers can encounter, are basically low-level criminals and veterans of multiple crimes. Most police officers will never encounter them once in their lives.
However, if there is really a criminal who "returns to the crime scene", he certainly cannot face it as a junior player.
Anyone who achieves this step can probably be described as being calm and unhurried.
The leisurely nature of murder scenes often means that traces are sparse.
The illumination surface of the footprint light source was about 1 meter wide and very deep, so Jiang Yuan swept over it piece by piece.
Wang Zhong, who came with him, saw Jiang Yuan move the light source twice, and immediately ran over and took over the task of moving the light source.
Jiang Yuan then thanked him, stood on a transparent footrest, supported his waist, and rested while observing the many footprints in front of him.
How could the police lose to criminals than "taking their time"?
In terms of technology, the police system has never won.
It is rare for police officers to be technologically advanced.
Most of the time, what the police have is "taking their time", which means hard work and iron feet, organization and execution ability.
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 their priority is also the lowest.
Some of the security guards' footprints still followed the previous footprints. It was obvious that this was the direction of the patrol.
Jiang Yuan was fortunate to have notified the team leader at this time. Otherwise, if he had come by himself, the security would have trampled the scene in advance, and it would have been difficult to organize security patrols in the future.
If the murderer is a security guard...
Jiang Yuan shook his head, but first focused on the footprints other than the security guards' leather shoes.
There are three sets of footprints here, two sets are relatively dull, and one set is relatively deep.
The two sets of Dan footprints are about 30 years old, and they are exactly the same as walking from top to bottom.
The deep footprints are from bottom to top, wandering back to the spot for several footprints, and then walking out from the inside out...
In fact, not only Jiang Yuan, but also several people present noticed the seemingly new footprints of this industry.
In fact, ordinary criminal cases are collected by ordinary criminal police or criminal police with the cooperation of on-the-spot investigation. In other words, taking footprints is the same as taking fingerprints, which is a basic skill of criminal police.
Moreover, at ordinary crime scenes, criminal policemen also selectively take fingerprints and footprints. Otherwise, not many technicians can bear the burden of taking all the fingerprints and footprints in the room.
That's why the wedding scene can be so luxurious.
As for now, facing the new footprints under our feet, everyone can see the problem.
This is what we have seen so far and is most likely the footprints of the murderer.
The direction of the footprints is also very revealing.
This person walked in from the 27th floor, stayed on the 28th floor for a while, then opened the fire door on the 28th floor and walked out.
If you go to the fire stairs on the 27th floor, you can see that this person came in through the fire door on the 27th floor.
He was running towards the 28th floor. If he wasn't the murderer, it would be too much of a coincidence.
"Doorknob." 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. It would be too late to retrieve them later.
Jiang Yuan stepped on the pedal and came to the fire door, turned on the light, and looked at the door handle first.
At first glance, it is a clean stainless steel door handle, the kind that is very reflective.
"It's been wiped." Jiang Yuan whispered.
Wang Zhong was stunned: "So careful?"
Jiang Yuan nodded.
Although I really want to find evidence, I have to say that it is becoming increasingly difficult to find fingerprint evidence.
The more careful perpetrators will take various measures to avoid leaving fingerprints. The simplest is to wear gloves, some wipe the touched areas, and some directly burn their fingers.
Wang Zhong looked a little disappointed, but Jiang Yuan could still accept it.
He looked at the footprints on the ground, slightly dazed.
If he was the only one present at that time, this guy would come out, put on gloves on his hands, lower the brim of his hat, and put on a mask...
"Can you tell your age and height from your footprints?" Huang Qiangmin stood outside and shouted.
Jiang Yuan quickly calmed down, took another look at the footprints, and said: "Male, age 45 to 49, medium build, about 170cm tall..."
Just like an ordinary person.
This is also the most troublesome part of footprint identification, as it shows too little specificity.
Huang Qiangmin followed Jiang Yuan's instructions and first sent a group text message. Then he saw that the people around him were in a bad mood and encouraged him: "There shouldn't be many people between the ages of 45 and 49 in this building. Let's look around first."
Jiang Yuan nodded lightly. Dust footprints still don't provide as much information as blood footprints. But no matter what, this can be considered a step closer.
As Huang Qiangmin said, the age range from 45 to 49 has narrowed 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 then he spoke.
epzw/html/15/15799/"Green Gourd Sword Fairy"
"I said one year old. If you're worried, just increase it by two years." Taking into account the age habits of different regions, Jiang Yuan followed Wu Junhao's wishes and relaxed it by two years.
However, in terms of accuracy of judgment, judging age through footprints is indeed not as accurate as judging height and weight.
Speaking of which, ordinary people can easily learn the simplest way to determine age through footprints.
It 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 years old, the center line is 30 years old, and the third line area is 31 to 39 years old.
The outermost fourth tier area is 40 to 49 years old.
When Jiang Yuan makes a judgment, he naturally has to combine other information, but it is only half the level.
"Multiple bands." Jiang Yuan shouted again.
Immediately, a policeman ran out and came back with a multi-band light source machine.
This thing also helps to 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 machine to 450 nanometer light and started searching near the fire door.
Maybe there will be fiber left.
However, it didn't.
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