National Forensic Doctor

25: Chapter 25: Frantic Wiping 25: Chapter 25: Frantic Wiping He cleaned the cups, then the glass, followed by the mirrors, cleaning the rough after the smooth, the fine after the rough, the soft after the fine, the hard after the soft…

The work of crime scene investigation, when looked at broadly, involves a variety of aspects, but delving into details, it consists of many minute tasks.

Policemen often say that solving a case is a matter of accumulating resources, and this is particularly evident during the on-site investigation phase.

Take for instance the collection of DNA and fingerprints.

Laypeople often believe that if a criminal suspect leaves DNA or fingerprints at a crime scene, the crime scene investigators will find them, but in reality, there is no advanced equipment capable of accurately detecting all fingerprints and DNA within a certain area.

Fingerprints, for example, come in three types: patent, plastic, and latent.

The first two types are visible to the eye, while the latter, as the name implies, require special means to be seen.

These methods vary depending on the material on which the fingerprint is found, and can involve different techniques such as powder, small tubes, fuming, chemical reagents, or varying chemical reagents…

Given this, to retrieve a fingerprint, a crime scene or trace evidence technician must first determine where fingerprints might be present, then observe—which can be done with the naked eye, aided by light or angle, by breathing on a smooth surface, or by using a magnifying glass or ultraviolet light.

Only after pinpointing the location of a fingerprint does the process of lifting it with powder or extracting it chemically with iodine fuming, silver nitrate, or other reagents begin.

Therefore, if there were truly a ‘Spiderman’ who had climbed across the ceiling, the likelihood of crime scene investigators finding fingerprints on the ceiling is quite low.

The complexity of DNA analysis exceeds that of fingerprint collection by far.

After all, fingerprints are visible; DNA sometimes can be seen, and sometimes it’s purely a matter of guessing.

For instance, it’s common to extract DNA from a victim’s toothbrush, but the officer performing the extraction cannot see anything—it’s merely a guess that DNA is likely present on the toothbrush.

For other items with a lower probability, such as shirts, bedsheets, or other personal clothing, or objects like cups and bowls, the presence of DNA is entirely a guess.

The strength or weakness of crime scene investigation skills becomes very apparent at this point.

Some investigators think from the perspective of the criminal suspect, guessing their movements and resting spots to find potential clues in an orderly manner, while others just pack up shirts and bedsheets indiscriminately to send back to the laboratory, or randomly cut out pieces without considering their relevance…

But in general, the more people involved in the investigation, the stronger their capabilities, and the more time and effort invested, the higher the probability of discovering clues and evidence.

In Wang Zhong’s view, Jiang Yuan’s operating techniques were very strong, but he felt it was only suitable during a homicide investigation.

For a mere theft case, conducting an operation like Jiang Yuan’s would be almost impossible.

The cost of processing a single DNA test, for reagents alone, is nearly 100 yuan, and the number of tests that can be performed in a given time is limited—there might be such a long queue for biological samples that it would be impossible to get to…

“Let’s clean the bathroom again,” Jiang Yuan said, having just finished processing the bedroom as the sky began to darken.

Wang Zhong, slapping his head and pointing to a large box full of evidence bags, said, “Why don’t we come back tomorrow?

There are already hundreds of these, and if we send them all to the lab, they’re going to lose their minds.”

Jiang Yuan explained, “More than half of these probably won’t yield any DNA, so they won’t use up any reagents.

The killer was too meticulous—look at the bedroom, so many fingerprints have been wiped clean.

Plus, with all the blood the victim lost, the killer must have spent a lot of time in the bathroom, rinsing mops and possibly even washing up or doing laundry.

The chances of finding DNA in the bathroom are quite high.”

“Xiao Hu and the others guessed the same and cleaned it thoroughly,” Wang Zhong said.

“They still cleaned too carelessly,” Jiang Yuan countered.

He had observed Xiao Hu and others’ handling of the body and saw no need for reservations now.

“Sigh…

alright, I’ll do an extra shift with you today,” Wang Zhong conceded.

He hadn’t noticed before, but now he was beginning to realize that the crime scene investigators on the team were indeed a bit haphazard, much like his own fingerprinting skills—the best review he could give was probably “functional.”

Just in the last few hours, the overlooked fingerprints that Jiang Yuan had found may not break the case, but they had already proved that his and Yan’s “functional” level was insufficient.

“Uh…” The old man at the door couldn’t sit still any longer.

“We need to go home for dinner.”

“Just sign here and you can go,” Wang Zhong, who hadn’t expected the elderly man to stay long to begin with, replied routinely.

Witnesses are often like this: either completely unwilling to get involved, or they wander about and talk aimlessly, or they lack patience.

Without the desire to educate, Wang Zhong simply brought over the crime scene inspection record, flipped to the signature page, had both men sign their names, then let them out the door.

He only cautioned, “What you’ve seen and heard today, you can only discuss in court or when questioned by relevant departments.

You cannot disclose it otherwise, or you’ll face criminal liability.”

The two old men left, impatiently nodding and saying “yes, yes, we know.”

Wang Zhong, used to this, nodded and closed the door, returning to assist Jiang Yuan with the DNA and fingerprint collection.

The poor lighting in the bathroom made the cleaning even more challenging.

But Jiang Yuan was energetically scrubbing away.

Becoming a level 4 crime scene investigator didn’t just improve his practical skills, but his cognitive understanding as well.

Various criminal theories essentially suggest one truth: the longer a criminal stays at a crime scene and the more they do, the more mistakes they are likely to make.

The perpetrator this time seemed to meticulously clean the crime scene and even calmly took a shower, but according to Jiang Yuan’s understanding, this only reflected the perpetrator’s amateurishness and arrogance.

With current DNA technology, even sweat can be used to identify someone, and it’s absolutely impossible to clean a bathroom to flawlessness in a very short time.

If the person had been even slightly professional, they should have at least wrapped the bathroom in plastic and carried away the plastic afterwards to bury or burn it, which would have resulted in far fewer traces of evidence.

However, that would have left traces of tape or adhesive…

Jiang Yuan wasn’t actually sure where he might pick up the perpetrator’s DNA.

He was young and had good stamina, so he scrubbed furiously.

Scrubbed.

Scrub scrub…

Jiang Yuan was still in the rookie excitement phase, having just acquired the crime scene investigation LV4 skill.

The scene he was truly investigating was the one before him.

Naturally, he took full advantage of the opportunity to practice and experiment.

In the skill set of crime scene investigation, technique is undoubtedly very important, meticulousness is indispensable, and on the other hand, physical strength, energy, and concentration are the keys to reaching a higher level.

Was it like how Xue Huaiyi fell out of favor with Empress Wu Zetian because he became too experienced and skilled, and was hence looked down upon?

Certainly not.

In the same way, the Zhang brothers wouldn’t lose favor for being young and reckless.

Wang Zhong was lacking in many of these skills, but although he was a bit weary, he made an effort to keep up, inspired by Jiang Yuan.

Jiang Yuan took particular care in cleaning the bathroom ceiling and corners.

The farther he went, the more meticulous and confident he became in his work.

This house didn’t have a separation between the dry and wet areas, but the bathroom was quite small, so the likelihood of water droplets splashing onto the walls and ceiling during a shower was not low, and it was impossible to thoroughly clean it in a short time.

The only question was whether he could pick up any DNA.

It was likely that any blood traces had been washed away or destroyed, but the perpetrator was probably an amateur if they thought all DNA traces could be washed away.

An ordinary person who commits an unplanned murder usually wouldn’t learn the relevant skills in advance.

Even if they did, they might not learn them thoroughly or diligently, and then it would be only natural for a diligent and well-trained police officer to catch them.

Night fell.

Jiang Yuan and Wang Zhong, carrying bags big and small, returned to the police station, heading straight for the DNA laboratory.

Nowadays, with the increasing number of cases being solved using DNA, the police department’s investment in DNA laboratories was also growing.

Even in a poor county like Ningtai, following various subsidies and policy guidelines, a DNA laboratory was established in accordance with the standards provided by the ministry.

This was also the department that consumed a lion’s share of the police budget, the three-person laboratory devouring over 10% of the annual funds, and it was still on the rise.

However, contrary to what Wang Zhong had expected, the DNA laboratory simply accepted the piles of evidence bags without any objections.

They didn’t even scrutinize or critique the biological samples Jiang Yuan and Wang Zhong brought in.

“How come ‘Old Qian’ from DNA has become so easygoing?” Wang Zhong followed Jiang Yuan to the forensic doctor’s office and mumbled his observation.

In the forensic doctor’s office, Wu Jun hadn’t gone home either, like most of the criminal investigators.

He sat in his office, organizing the data collected during the day.

Standing up to rub his eyes, Wu Jun slowly said, “The captain was angry this afternoon.

The problem now is the lack of clues.

The DNA lab is eager for you guys to send over samples so they aren’t left with nothing to do.”

Jiang Yuan laughed upon hearing this, “Not working at night means having nothing to do?”

“The captain hasn’t gone home,” Wu Jun said.

“If they don’t find something soon, they will have to reassess the scene themselves.”

Wang Zhong looked at Jiang Yuan, clicking his tongue twice, and said, “It would be a waste of time for them to go.

With their level of crime scene investigation, and I don’t mean to brag, they could handle mundane cases, but…”

Wu Jun cut off Wang Zhong, “You think they don’t know that?”

“Uh…” Wang Zhong found himself at a loss for words and quietly returned to his own office.

Jiang Yuan, on the other hand, was quite satisfied.

He tidied up and laid out his cot directly in the office.

It wasn’t until noise disrupted the detectives who had been up all night.

“The DNA matched someone, and Captain Liu has taken a team,” Wang Zhong was the first to burst into the office, his eyes still rimmed with rheum.