1995, Starting as a Criminal Investigation Expert

According to the 84 regulations on the management of gun and ammunition traces, it is required that the same gun and the same batch of bullets be fired 3 to 5 times, and then photographed for record-keeping.

The key is to preserve the warhead and cartridge case without damage.

The conventional method is to use cotton, paraffin wax, or even rubber as bulletproof materials to protect the bullet as much as possible.

There are also similar gun barrels and bullet catchers.

The structure might just be a box filled with material, and you just shoot it in.

A handgun has limited power, so this operation can be performed indoors.

But rifles won't work; it's best to use them outdoors.

There are many methods, but the simplest one is to make a big puddle and shoot into it.

Water is the most perfect bulletproof material.

Sandbags are also acceptable, especially the finest river sand. After firing, the river sand causes minimal wear on the bullet and concentrates at the tip, having almost no effect on the most important identification marks, such as rifling.

Moreover, using sandbags eliminates the risk of ricochets.

There was a specific area in the courtyard used for testing long spears.

The process was quick; Li Shu picked up his gun and used the magazine he had found on the spot to fire directly at the sandbag.

Multiple warheads and cartridge cases were quickly recovered.

They were brought back, washed and dried, and examined under a microscope to find the few with the best conditions, in preparation for making molds and keeping records.

Li Shu watched Zhao Yong busy at work.

The marks on the cartridge cases are at the micrometer level, so direct photography is definitely not feasible; a transfer process is necessary.

There are many similar transfer methods.

For example, a cellulose acetate film, which is basically a plastic film, is used to apply pressure to the bullet and roll it around.

The film needs to be softened. In the past, it was directly heated, and later it was soaked in acetone solution.

The purpose is the same: to transfer the fine marks on the bullet head onto the plastic film during the rolling process.

Later, research also found that varnish was used. In metallographic research, varnish is applied to protect the sample, so there are some specially made varnishes that can form a coating on the bullet.

Next comes the liquid method that Zhao Yong is currently using.

Cellulose acetate films are brittle. In 92, someone prepared a solution based on cellulose acetate and used a liquid curing method to achieve transfer printing.

It's easier to operate and the transfer effect is better because it's a liquid that seeps into every mark.

Seeing Li Shu staring intently, Zhao Yong said, "Why don't you give it a try?"

This method was only invented in 92, and there is still a process of promotion. Li Shu may not have been able to learn it even at the police academy.

Practical experience can help you gain more expertise.

Li Shu shook his head to indicate that he did not need it.

Tan Guoxiong was interested, and Zhao Yong gave up his seat to teach him the specific operating method.

Li Shu watched silently from the side.

It's not that I'm not interested; firearms and ammunition identification is also a very important category in criminal science and technology.

Especially now there are a large number of gun-related cases.

However, after reviewing the information from the system, I felt rather uninterested in the method at hand.

Based on the information I've read, bullet wound identification, like fingerprint identification, has a crucial dividing line.

That is the integrated ballistics recognition system.

It's called the IBIS system abroad, and it was first developed by Canada a few years ago.

It is similar to AFIS, which converts bullet marks from three-dimensional to two-dimensional images according to certain standards, and then uses computers to quickly compare them.

It solves the pain point of low efficiency in hand-rubbing, just like fingerprint comparison.

Based on the information provided, it seems that related research also began in China in the last two years.

And there's one person we need to mention here.

He is a bullet hole identification expert; the system has omitted his name.

There is an introduction that says this person, around 2000, developed an efficient and low-cost method for extracting bullet marks, and based on this, developed a domestically produced bullet mark comparison system.

Therefore, 2000 was a watershed year.

The new method was like a game-changer, completely overshadowing all previous methods and rendering them obsolete.

Of course, this method will become outdated if we continue to use it.

Later, when the technology became more advanced, there was even 3D scanning. Just looking at the information, Li Shu felt that the descriptions were like science fiction.

As he looked around, a bold idea suddenly popped into Li Shu's mind.

Could I have developed this system a few years earlier?

The system has all the relevant information, and Li Shu believes that as long as he obtains certain funding and personnel support, it is entirely possible to achieve this.

Lost in thought, they extracted the impression and sent it to the darkroom for photography.

We'll discuss the comparison tomorrow.

Li Shu and Tan Guoxiong left work early. They had both experienced quite a bit today. In Han Jianjun's words, "Don't overthink it when you get home. Get a good night's sleep, and everything will be fine tomorrow."

Riding his bicycle towards the dormitory, Tan Guoxiong suddenly said at the door, "Your mother is here."

Li Shu looked up and saw his family's Santana parked downstairs.

With a quick glance around, Li Shu said hastily, "He probably heard the news. Don't let it slip."

If Hu Xiaojun knew that I was on the front lines of the arrest, she would probably nag me endlessly.

Tan Guoxiong nodded hurriedly.

Hu Xiaojun would come over whenever she had free time to help the two of them tidy up the house and bring them delicious food. To make things easier, they gave her a key.

Upon entering, I discovered that not only my mother had come, but my father, Li Weiqiang, had also arrived.

The situation escalated to the point where grenades were even used, and the two men heard the news.

"Mom, I'm a technical police officer. Even if they use rockets, it has nothing to do with me," Li Shu said.

Hu Xiaojun thought about it and agreed.

Li Weiqiang, his face flushed from drinking, said, "I told you, it's nothing, but you insisted on coming. But son, you can't be afraid to go in dangerous situations just because you're a technical police officer. Don't forget, you're a policeman."

Li Weiqiang dreamed of joining the army when he was young, but he didn't get the job, which he regretted for the rest of his life.

He actually strongly supported Li Shu becoming a policeman.

In his mind, police officers should rush forward when they encounter danger.

If you don't flush, do you expect the people to flush?

"Why are you rushing around? How many lives does your son have?" Hu Xiaojun scolded.

Tan Guoxiong, standing nearby, smiled without saying a word, thinking to himself that Li Shu not only rushed forward but also shot at the suspect.

I went to work the next day.

First, compare the bullet marks on the two guns.

The workload is manageable.

The May Fourth rifle was extremely common; at least half of the gun and ammunition files kept by the bureau were of the May Fourth type.

Cases involving the use of the Type 56 assault rifle are much rarer; many of the files are records of the firearms kept by the relevant units.

Since these guns were not reported lost, there is no need for comparison.

With this screening process, only a few dozen files needed to be compared, and the comparison was completed in a short time.

Unfortunately, the comparison failed.

This Type 56 submachine gun was never fired in Nanjiang.

As for this Type 54 pistol, let's first compare it with the bullets extracted from the Yanglu Lane case.

This job will be done quickly.

As expected, the comparison was successful; the bullets that killed Huang Youjun and Kang Guiying were fired from this Type 54 pistol.

As for whether there are other criminal records, that needs to be compared further.

I was busy in the morning when Xu Qiang came looking for me.

I was overjoyed to hear that the May Fourth Movement style had been compared with it.

With fingerprints and bullets, the Yang Luxiang family annihilation case can be considered solved.

I didn't quite get the fifth and sixth moves right, but I didn't react much.

He was mentally prepared, after all, in his memory, there were not many Type 56 submachine guns involved in gun-related cases in Nanjiang.

"Here's what you'd like to do: send the bullet marks from this Type 56 rifle to Yuehai for comparison," Xu Qiang said.

He thought carefully about Xiao Rui's idea yesterday.

I think Zheng Cheng might actually have a criminal record.

Since no match has been found for this gun in Nanjiang, it is very likely that Zheng Cheng committed the crime in another province or city.

After careful consideration, the most likely candidate is Yuehai.

After the incident yesterday, Xu Qiang reviewed Zheng Cheng's situation and noticed that his neighbors and friends reported that Zheng Cheng had traveled to and from Guangdong and Shanghai many times in the past.

It even predates the time he partnered with someone to open that video store.

This was not difficult; a letter of assistance was faxed to the Guangdong Provincial Department of Public Security that same day.

As it turned out, there was indeed something going on.

The next day, Yuehai urgently contacted the team.

It was only then that I learned that, starting in 89, five armed robberies had occurred in two other cities, Yuehai and Yangcheng, over several consecutive years.

The robbery, which involved stealing over two million yuan, resulted in three deaths and six injuries, and the case remains unsolved.