"Yes, those two murderers have not been caught. It's been twenty-two years...... Luo Fan sighed with emotion, "Actually, that case happened in my hometown. I was four years old and didn't understand anything. But I know that there are people who will suffer all their lives for those lives that have been lost......"

"Jixiang Hotel" is located at No. 183, Huiquan Street, Xiuli Town, Zhejiang Province, and is a small three-story white building with an inconspicuous appearance. The owner and hostess who run the inn are a warm-hearted and kind young couple with a good reputation in the local area.

In the early morning of November 20, 1995, two suspects staying in room 204 of the Jixiang Hotel first had ill intentions towards Li, a Shandong businessman who lived in the same room, and killed him in his sleep. Because Li sewed most of the cash he carried with him into the inner pocket of his autumn pants, the two did not loot too much property, so they started the idea of the hotel owner again.

Under the pretext that the "light bulb" was broken, they tricked the boss into killing him in room 204, and then broke into room 201 and looted the cash register. The proprietress and daughter of the hotel happened to live in room 201 and were sleeping at the time of the crime, but because the little girl woke up halfway through and woke up the proprietress with a cry, the murderer ruthlessly killed the two.

Unfortunately, the boss's mother got up early in the morning to go to the toilet and encountered two murderers in the corridor who were about to escape, but she did not survive.

Through investigation, the police extracted the fingerprints left on the glass by the two suspects in room 204. In addition, a shoe print on a pile of clothes on the ground also provides a more valuable clue.

The pattern of the shoe print is in the shape of a hexagonal diamond, which has never been seen in the surrounding clothing trade market. Whether it is the police or the informant, when they enter the room, they will carefully bypass the pile of clothes scattered on the ground, so the shoe print can only be left by the murderer when he panicked.

According to the descriptions of other guests at the hotel, the police roughly grasped the physical characteristics of the two suspects: one of them was about 40 years old, about 1.65 meters tall, slightly chubby, and had a large round face; The other person was younger, about 1.8 meters tall, with dark skin, slender eyes, and a cap. Both speak with accents from the Anhui region.

Unfortunately, in the mid-nineties, when information technology was not yet widespread, surveillance was a scarce commodity. Jixiang Hotel does not strictly enforce the accommodation registration system, and even if you don't have an ID card, the owner will check in the guests. Therefore, the police could not get further information about the two "disappeared guests".

Half a month later, the large-scale investigation began. The soldiers of the task force were divided into two routes, one went to the southern Anhui region to compare fingerprints, and the other went to investigate the source of the special shoe print.

In 1995, when the case occurred, the electronic fingerprint identification system had not yet been used, and fingerprint comparison was all based on visual identification. A place's fingerprint bank is usually a stack of cards with black stripes on a white background. If Curry doesn't have the fingerprints of the target, the police have to walk the streets to visit them.

In order to find the two "disappeared guests," the task force traveled to most of China, as far as Shanghai, as far as Guangdong and Yunnan. Whenever there are cases with similar modus operandi or circumstances elsewhere, they will go to see if they can join the cases.

On the eve of the Spring Festival in 1996, at Shuiximen in Nanjing, two investigators walked aimlessly between various shoe stalls. Suddenly, a pair of high-top hiking shoes caught their attention, and they turned the soles over to look at them, and the results turned out to be exactly the same as the shoe prints at the scene.

After investigation, the hiking shoes were made in Kunshan, a South Korean-owned company, and exported to Canada, and the stall owner sold the only box that was accidentally left before shipping to the sea. In addition, the factory used to distribute some defective shoes to employees as benefits.

However, when investigators rushed to Kunshan, they found that the company had hundreds of employees, not to mention the migrant workers who had come and gone over the years. Therefore, the owner of the shoe print is not necessarily an employee of the shoe factory, but may also be a related person of an employee. For the task force, the scope of such an investigation is too large, and it is like looking for a needle in a haystack.

The progress of the case has reached an impasse......

"I remember you also mentioned cigarette butts at the crime scene in your book." After listening to Luo Fan's true description of that case, Gu Song thought of the plot in the novel.

"Oh?" Luo Fan turned his head and glanced at Gu Song, "Have you really read that novel?" I thought you were just being polite to me. ”

Gu Song smiled embarrassedly and said, "I really didn't see it when I met you the first time, and I went back to make up for it later." ”

"I see." Luo Fan shook his head with a smile and continued, "Back then, the task force found a total of 26 cigarette butts at the crime scene. One cigarette case stands out, with the brand name 'Sheng Tang' printed in red on the golden packaging. This is not a mass brand, it is produced in Wuhu Cigarette Factory in Anhui Province, and it is generally only common in southern Anhui. Although there was no way to identify the biological information on the cigarette butts, the investigators carefully collected and stored all the cigarette butts.

"With the development of science and technology, DNA technology has become more and more mature, and these physical evidence, which has been carefully preserved for more than 20 years, finally come in handy. However, DNA is easy to detect from fresh samples, but physical evidence that has been preserved for so long can lead to a loss of DNA information due to severe degradation. Moreover, the samples extracted back then were stored together, and there was also the problem of mutual contamination.

"After more than a week of hard work in the DNA lab, the team finally succeeded in extracting the DNA of 10 people from those cigarette butts. The special case team revisited the unrelated people who were present at the scene and found out the suspects No. 1 and No. 2. Suspect No. 1 lost six cigarette butts, and Suspect No. 2 lost nine cigarette butts, and it happened that the cigarette butts lost by these two people included 'Shengtang brand' cigarettes produced in Wuhu, Anhui Province.

After that, the task force took the two hard-working DNA extracts and first went to the national criminal DNA database to investigate, but found nothing. Then, they went to the DNA databases of various provinces and cities, and the results were just as disappointing.

Just when the task force was cornered, the Gansu silver murder case that had been deposited for 30 years was successfully solved, and they also wanted to try to use Y-DNA chromosome testing technology to find the suspect. In fact, this is how the case really happened. So far, the identities of the two suspects are still unknown......"

"But at the end of the novel, you hint to the reader that the police have found a man surnamed Guan in a DNA database somewhere. Compared to the DNA of Suspect No. 2, they were related more than a dozen generations ago. Although the police investigation is still difficult, you have at least given the reader a glimmer of hope. ”

"Well, that's how I wrote it in the novel......" Luo Fan looked at the flickering street lights outside the car window, and said thoughtfully, "I hope in reality, this case can end sooner......

Note: Y-DNA chromosome testing technology uses the Y chromosome to be passed down from male to paternal line. If a male suspect leaves genetic material at the scene of the crime that can detect the DNA component, Y-STR (sho) is performed by finding relatives who have the same Y-DNA origin as the suspect

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epeat, short tandem repeat fragments) can directly determine the suspect's last name. Each surname has a specific signature on the Y chromosome, like a "barcode" that flows in the blood to represent the origin.