National Forensic Doctor
Chapter 401 - 401 368 The 4th Person

401: Chapter 368: The 4th Person 401: Chapter 368: The 4th Person The urine of a normal person is usually colorless, transparent, or slightly yellow, and although it contains a large amount of metabolic waste, it is free of bacteria, so it can be drunk.

Furthermore, normal urine is weakly alkaline, so if a person who pursues health must drink weakly alkaline water, urine can also be one of the choices.

At the same time, urine can provide a great deal of information.

Hospitals can use it for urinalysis, and forensic departments can use it to extract DNA.

Urine contains a small amount of exfoliated cells, which can be used for DNA comparison.

However, amateurs look at the threshold, while professionals should not feign ignorance.

It’s true that DNA can be extracted from urine, but it’s much more difficult than from blood.

To start with, the number of exfoliated cells in urine is relatively low, which means a larger volume of urine is needed for convenient extraction.

On the other hand, urine at the scene is obviously not well-preserved.

Good urine suitable for DNA extraction should be stored at low temperatures.

Therefore, in the early years when DNA technology was first popularized, which is the first decade of the 21st century, extracting DNA from urine was very difficult, and there were very few such cases.

At that time, DNA comparisons were mainly based on blood and cerebrospinal fluid, followed by toothbrushes and cigarette butts for oral epithelial cells, occasionally some hair, which had to include follicular tissue.

Nowadays, technology has improved, and the richness of DNA comparison has increased significantly.

Not only is follicular tissue no longer needed for hair, but the requirements for extracting DNA from urine in top-notch DNA labs have also become much lower.

By the way, here’s a piece of trivia: if a man or woman suspects that a child is not theirs, there’s no need to take the child to an institution or to draw blood and leave a trace.

Just have the child pee a collectible amount, chill it with ice-cold cola, and send it to the relevant testing institution, and the results will be obtained quickly.

For criminal suspects, this is naturally even more convenient.

Jiang Yuan collected as much of the urine stains as possible with the cotton swab he had dampened in front of him, then combined several cotton swabs together, wrapped them in filter paper, and folded them into a neat triangle.

This method maximized the preservation of the integrity and authenticity of the urine, just like collecting bloodstains.

Several crime scene technicians from Chi Yong City watched Jiang Yuan’s operations, somewhat confused by his approach.

To be honest, Jiang Yuan’s operation this time had no mysterious aspects; it was just the most basic and cautious method, leaving the others unable to critique it as either good or bad.

However, it seemed that the case had made progress, which was a very tangible result.

“Let the DNA lab expedite this,” Jiang Yuan said, handing the urine sample to the crime scene technician behind him, and continued searching in the bathroom.

Liu Jinghui interjected at this point, saying, “There’s a ninety percent chance that this person is strongly connected to the case, probably a participant or someone with knowledge of it.”

The captain was now only concerned about the case and immediately asked, “How so?”

Liu Jinghui explained, “This is the hideout of a three-person gang, which is to say, it’s where they prepared for the robbery and processed the stolen goods.

Besides the three people and the participants, it’s not likely to be used for entertaining guests.”

The captain nodded again and again.

He wasn’t particularly skilled at solving cases or, to put it another way, he had certain investigative capabilities but was more focused on management and had gradually moved away from frontline leadership.

If he had to make a similar judgment himself, even the captain wouldn’t trust his own conclusion, but when Liu Jinghui spoke, the captain’s mood immediately changed.

“So you’re saying, in reality, there should be four perpetrators?” The captain exerted his brain power to add 3+1.

Liu Jinghui glanced at Jiang Yuan and smiled, “At the crime scene, which is the victim’s home, there were definitely three criminals.

As for the owner of the urine we just found, my guess…

well, a guess, is that they were likely involved in disposing of the stolen goods.”

The captain was startled, “Involved in disposing of the stolen goods?

Why?”

The answer was somewhat unexpected.

Liu Jinghui slowly explained, “First, this person doesn’t seem like an accomplice.

All three suspects are at an age where they can piss against the wind, all strong and capable young men.

This person can’t even pee straight; what use is such an accomplice?

Just to share in the profits.”

“Secondly, it’s possible they could be the mastermind.

But considering the safe, they didn’t provide the necessary equipment, like an oxy-acetylene cutter for instance.

If there was a mastermind, they should be the one to purchase it or find it.

But our investigation is quite clear, the three of them went to the scrapyard together to buy the cutter, which shows they don’t trust each other or this person.”

“Thirdly, this individual appeared at the gang’s hideout, which must be because the three needed him; otherwise, they wouldn’t disclose the location.

What do three young men who have just committed a major crime and are preparing to flee need the most?

Nothing more than money, documents, and a getaway plan.”

As Liu Jinghui spoke, he raised his chin slightly, “Although from our perspective, documents and getaway plans are certainly more difficult to come by.

In reality, the most valuable and hardest to obtain is still money.

There was very little cash in the victims’ house; the main items lost were jewelry, gold, watches, antiques…

The three must convert these items into cash before they can flee, so at this moment, what they need most is someone to fence the stolen goods.”

“Makes sense, makes sense…” The captain nodded repeatedly.

He now saw the hope of solving the case, and listening to Liu Jinghui was incredibly pleasing to the ear.

Their conversation ended, and the room fell silent for a while.

Liu Jinghui and the captain both frowned involuntarily.

Something about the atmosphere was off.

During a crime scene investigation, it’s normal for there to be occasional talking or even chatting.

It’s like finding a used condom and then a piece of hardened toilet paper; you need to exchange information to determine whether the room witnessed one round of sexual activity or two.

Just now, the crime scene technicians had been quietly muttering to themselves while following Jiang Yuan, creating a background noise similar to that of a forest.

But their sudden silence, just like a forest becoming deathly still, was clearly unreasonable.

Liu Jinghui and the detachment leader leaned in closer and saw that several birds… no, several crime scene technicians were stretching their necks to look at something in the doorway of the bathroom.

Further inside, they saw Jiang Yuan holding a tablet, making various gestures with it.

“What is this… for?” the detachment leader asked curiously.

“Separating overlapping fingerprints…” The oldest crime scene technician turned to look at the detachment leader, his eyes clearly betraying a hint of despair.

The detachment leader was taken aback, “You’ve found an overlapping fingerprint?

How do you separate it?”

“Exactly,” the technician repeated.

Liu Jinghui glanced at Jiang Yuan and asked quietly, “What are we doing now?”

“I found a few fingerprints on the toilet, they all overlapped when I lifted them, and I want to separate one to see if it matches this fourth person,” Jiang Yuan explained plainly.

The fingerprints in this rental room were numerous and chaotic.

Considering that the gang of three had only rented it for a short time, one could imagine that most of the fingerprints in the room likely came from the landlord, previous tenants, and so on.

Although it was possible to collect all these fingerprints and filter them after a concentrated comparison, Jiang Yuan had his methods and was not willing to wait that long.

After all, DNA had already been collected and it was the most convincing evidence; the main purpose of collecting fingerprints now was to be quick.

In pursuing fleeing criminals, being one hour faster is indeed an hour gained.

One must not provide the criminals a chance to breathe.

Only by making the fugitives feel suffocated can the chase be successful.

Therefore, Jiang Yuan’s choice was simple.

He directly lifted the fingerprints from the flushing button of the toilet.

The fourth person had urinated in the toilet and, normally speaking, should have pressed the flush button, so there was a high probability that the fourth person’s fingerprints would be on it.

At the same time, the flush button would also bear the fingerprints of the other three, or even more people.

Now, the problem was that overlapping fingerprints simply couldn’t be distinguished nor matched by software—but this was only the perception of the ordinary crime scene technicians.

At Jiang Yuan’s level, as long as he wished, he could separate the fingerprints through their ridge characteristics.

The process was not very easy, but Jiang Yuan was capable of doing it.

However, this scene was truly disheartening for the ordinary technicians—such skills, without a bit of natural talent and divine favor, were very hard to learn.

Even Jiang Yuan had to analyze the ridges one by one.

Current fingerprint technology could theoretically separate overlapping fingerprints through software, but the error rate was too high, rendering the separated prints practically unusable.

Against a knowledgeable lawyer, it was easy to be publicly embarrassed in court.

At this point, the most reliable method was still manual, and the difficulty was extraordinarily high.

Yet, Jiang Yuan could do it with just a tablet, making it seem easy.

After marking a couple of groups of characteristic points, Jiang Yuan soon matched one out of the dozen, identifying a person.

“Lei Fuhan.

This man has a prior record of dealing stolen goods and also forges documents…

a complete set of skills,” Jiang Yuan read out the matched information, feeling as though this individual was tailor-made for the role.

The detachment leader slapped his thigh hard, “Did the gang of three buy their fake documents from him?”

“Very likely,” Jiang Yuan nodded.

“It’s definitely that.

He fences and provides documents!” The detachment leader was already impatient.

If the trio had purchased their identity documents from the fourth person, then catching Lei Fuhan would easily confirm the trio’s current whereabouts.

Once they were caught, the whole case would be perfectly concluded.

The more he thought about it, the happier the detachment leader became; he grabbed his cellphone and started making arrangements.

At this stage, Jiang Yuan’s judgment was in sync with his, and he merely turned to Mu Zhiyang and said softly, “You can buy a high-speed train ticket home now.”

…