National Forensic Doctor
Chapter 159 - 159 154 Footprints

159: Chapter 154 Footprints 159: Chapter 154 Footprints The dust fixative purchased by the Ningtai County Bureau was made using a solvent of alcohol mixed with rosin.

It’s quite an old-fashioned fixative; its transparency is slightly poor, and the drying and fixing time is long.

Jiang Yuan sprayed a row of fixative in the stairwell; the footprints in the back were clearly visible only after those in the front had been gradually sprayed.

At this point, an ordinary crime scene investigator or trace examiner would typically sprinkle some powder to reveal the prints.

Jiang Yuan didn’t need this step; he just looked at the footprints and savored their originality.

But he only took a brief look.

Most of the footprints were likely left by the security guards.

The security guards at Wanghe Building all wore leather shoes and small ties—they were not very practical, but they looked quite official.

Jiang Yuan continued spraying fixative and placed the transparent forensic stepping board on an area without footprints, moving forward step by step until the stairs between the 27th and 29th floors were completely covered.

Next, Jiang Yuan set up the specially transported forensic footprint light source.

“Forensic footprint light source” sounds like a very professional piece of equipment, but in reality, it’s just a high-powered LED light with a casing that allows for reasonable height and rotational angles.

Of course, a lithium battery is essential, as it meets the demands for portability and battery life when used outdoors, and also ensures a proper price and profit margin.

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.

When shone onto the floor, the footprints where fixative was freshly applied were revealed in all their minute details.

Looking for footprints, fingerprints, or trace evidence actually involves a similar set of tools.

The tools are indeed quite good and convenient, but before this, Jiang Yuan could hardly be bothered to bring them over.

Like today’s fall scene, which was just a few meters away, Jiang Yuan used natural light during the day and a portable light source in the evening to find a lot of trace evidence, feeling that there was no need for such a large light source.

However, in the current situation, if they really encountered a criminal “returning to the crime scene,” they would naturally use whatever equipment they had on hand.

A typical murder case, or rather, the kind of murder that regular police can encounter, is usually the work of amateur criminals.

Serial offenders, experienced in multiple crimes, are something most police officers might never come across in their lifetime.

But if there were indeed a criminal “returning to the crime scene,” one could not confront them as if they were a novice.

Anyone who reached this step could generally be described as calm and composed.

And at a crime scene, calmness often means sparse traces.

The footprint light source had a wide illumination area of about 1 meter, although its depth was quite vast, so Jiang Yuan scanned the area bit by bit.

Wang Zhong, who had come along, saw Jiang Yuan move the light source twice and immediately ran over, taking over the task of moving the light source.

Jiang Yuan thus expressed his thanks and then stood on a transparent footplate, supporting his waist while resting and observing the many footprints before him.

Compared to “calmness and composure,” how could the police lose to a criminal?

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

Having the lead in technology is something very rare for the police.

Most of the time, what the police have is “composure,” meticulous effort, and perseverance; it’s about organization and implementation.

Jiang Yuan restrained his desire to make rapid judgments and reviewed each footprint one by one.

The security guards’ footprints were the most numerous, but they were also of the lowest priority.

Some of the guards’ footprints were even stepping on the ones before them, from which one could infer the direction of their patrol.

At this time, Jiang Yuan was also grateful for having notified the squad leader; otherwise, if he had come by himself, not only would the scene have been trampled by the security beforehand, but it would also have been difficult to prevent the guards from patrolling later on.

If the murderer was a security guard…

Jiang Yuan shook his head, deciding to first focus on the footprints that weren’t from security guards’ leather shoes.

There were three sets of footprints here, two sets were faint, and one set was deep.

The two faint sets were approximately of someone around 30 years old, showing a top-down walking trail.

The deep footprints were from bottom-up, hovering in place for several steps, then walking out from inside to outside…

In fact, not just Jiang Yuan, but several people at the scene had noticed this line of noticeably fresh footprints.

In common cases, it’s usually ordinary detectives or forensic technicians who collect such evidence, meaning that collecting footprints, like collecting fingerprints, is a basic skill for detectives.

Moreover, at common crime scenes, detectives also select fingerprints and footprints to collect; otherwise, if they were to collect all fingerprints and footprints in a room, there wouldn’t be enough technicians to handle them.

It’s only at a murder scene that one can afford such luxury.

As for now, facing the row of fresh footprints beneath their feet, everyone recognized there was a problem.

These were the footprints that, to date, seemed most likely to belong to the killer.

The direction of the footprints also said a lot.

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

And if one went to look at the fire escape on the 27th floor, it becomes clear that this person came in through the fire door on the 27th floor.

Heading straight for the 28th floor, if it wasn’t the killer, that would be too much of a coincidence.

“Door handle,” Wang Zhong reminded Jiang Yuan in a low voice, suggesting he check for fingerprints first.

Jiang Yuan nodded.

There were multiple footprints on the ground, so it could wait to collect them later.

Jiang Yuan then stepped over to the fire door, turned on the light, and checked the door handle first.

At a glance, it was a clean, stainless steel door handle that was particularly reflective.

“It’s been wiped.” Jiang Yuan said softly.

Wang Zhong was startled, “That meticulous?”

Jiang Yuan nodded.

Although they were eager to find evidence, it couldn’t be said finding fingerprint evidence was getting more and more difficult.

Perpetrators with even a modicum of forethought would employ various methods to avoid leaving fingerprints.

The simplest was wearing gloves, sometimes wiping the areas they touched, and there were even those who burnt their own fingertips.

Wang Zhong looked somewhat disappointed, but Jiang Yuan could accept it.

He stared at the footprints on the ground, slightly absent-minded.

If they were the only ones present at the time, and that guy walked out again, with gloves on, the brim of his hat pulled down, plus a mask on…

“Can you tell the age and height from the footprints?” Huang Qiangmin called out from the perimeter.

Jiang Yuan quickly refocused and took another look at the footprints.

“Male, age between 45 to 49, of average build, approximately 170 centimeters tall…”

Just an ordinary appearance.

This was also the most troublesome aspect of footprint identification; the specificity it could reveal was just too little.

Following Jiang Yuan’s lead, Huang Qiangmin sent out a group text message and then, seeing that people around were not in a good mood, encouraged, “People between 45 to 49 years old should not be numerous in this building.

Let’s start looking.”

Jiang Yuan nodded slightly.

Dust footprints weren’t as informative as bloody footprints.

Nevertheless, this was a step closer.

As Huang Qiangmin said, narrowing down to the age range of 45 to 49 had already reduced the scope significantly.

“Is the age accurate?

Do we need to broaden the range a bit?” Wu Junhao, who had been standing nearby, finally spoke up.

“I was referring to full years of age, but if you’re concerned, we can broaden the range by two years,” Jiang Yuan considered regional age-counting differences and accommodated Wu Junhao’s suggestion by relaxing the age range by two years.

However, in terms of accuracy, determining age through footprints was indeed not as reliable as estimating height and weight.

To speak of it, the simplest method of estimating age through footprints is something anyone can easily learn.

It involves dividing the footprint vertically into four equal parts, where the innermost first line indicates an age range of 18 to 23 years, the second line indicates 24 to 29, the center line represents 30 years old, the third line is from 31 to 39, and the outermost fourth line is 40 to 49 years old.

When Jiang Yuan made his assessment, he naturally took other information into account, but getting it half right was generally close enough.

“Multispectral.” Jiang Yuan called out again.

A police officer immediately ran out and brought back a multispectral imaging device.

This device was also an aid in finding trace evidence.

It was particularly useful for locating microscopic evidence.

Many objects emit fluorescence under the right wavelength of light.

Jiang Yuan adjusted the multispectral imaging device to a 450-nanometer wavelength and began searching around the fire door.

Perhaps some fibers had been left behind.

However, there were none.