The autopsy proved that the deceased had indeed died of suffocation due to neck compression.

The autopsy report presumed the time of victimization of the deceased to be between 11 p.m. and 12 p.m. on 5 September. The autopsy report also confirmed that the victim's lower body contained male semen, which led to the man's blood type B.

According to the investigation near the station, You Meiyun did get off the tram at 11:06 last night. At the same time, people with such criminal records who lived near the scene were also investigated.

In the suburbs alone, there are fifteen or sixteen people who are frequent offenders: rapists, perverts who steal women's underwear. And the hooligans.

All those with criminal records were brought to the criminal investigation detachment for the purpose of interrogating their alibi. As a result of the interrogation, people with blood type B have alibi; For people whose on-site evidence is not clear, the blood type is not type B. Therefore, all those with previous convictions are excluded.

You Meiyun has two close friends at the Xingda Trading Company where she works. These two people are not her lovers, just boyfriends. Despite this, the police still went to investigate their "alibi". A more thorough investigation was conducted on the 30-year-old section chief with blood type B. But at the moment when You Meiyun was killed, the section chief was playing mahjong with a friend, which has been confirmed.

The rest is the boyfriend You Meiyun met on Hainan Island. According to You Meiyun's girlfriend, You Mei went to say that she had played adventure games with a young man when she was on Hainan Island. When searching You Meiyun's room, she did find photos taken while she was on vacation on Hainan Island. The photograph shows a young man, tall and long-haired, aged about twenty-seven or eighteen. It looks very strong. He was dressed in swimming trunks and stood side by side with You Meiyun, who was wearing a bikini, smiling.

Following this clue, the criminal investigation detachment contacted the hotel on Hainan Island to learn some details about the hotel stayers at that time, so that a week had passed unconsciously.

5

When he got off work on September 25, staff member Li Yuan went to watch an American science fiction film. As a result, it was past 10.30 p.m. when he got off the bus near his residence. On the way home, I passed by the sports field of a university. Walking to a secluded place, suddenly, a dark shadow rushed out of the darkness. Li Yuan screamed in surprise, and then was knocked to the ground by the black shadow, and the cigarette on his mouth flew out.

"Bastard!"

Li Yuan scolded and got up from the ground. He felt a sharp pain in his left arm, and when he touched it with his hand, blood dripped down his fingers. He was stabbed by the man who knocked him down.

Li Yuan quickly ran into the nearby police station, asked for a hemostatic bandage, and reported the situation to the police. When the police heard the news, they immediately picked up a flashlight and came to the scene with Miki.

The policeman turned on his flashlight and asked while looking at the place where Li Yuan fell, "Do you see the other party's face clearly?" ”

"No, because I stopped to light a cigarette, it was windy, and I covered my head with my hands and lowered my head to light the fire, so I didn't even bother to look at the other person's face and was knocked down."

"Did your wounds be cut by the murderer?"

"Yes."

"The murderer is tall?"

"I don't see it clearly, maybe it's similar to me. 1.70 meters or so. ”

"How big is that guy?"

"Judging from his strength, he can't be an old man, I weigh 130 pounds, and he knocked me down at once."

"Hmm."

"What is he doing in that dark place in the middle of the night?"

The policeman shone a flashlight at the dark place as he walked over. Li Yuan also followed.

Suddenly, the policeman said, "Ah! The ground screamed, and the circle of the flashlight stopped on the body of a naked woman lying on the ground in the shape of a "big". This is a young woman, completely naked, and the white marks of the bikini are especially vivid on the tanned skin.

Li Yuan watched from behind the policeman.

The policeman bent down to take her pulse and listened carefully with his ear to his chest.

"Dead?"

Li Yuan asked in a trembling voice.

The police did not answer the questioning, still examining the body, and finally stood up and said to Li Yuan:

"Please wait here."

As he spoke, he handed the flashlight to Li Yuan. "It's a homicide case, I'll report it to the Public Security Bureau immediately."

When the police called, Li Yuan shone the circle of his flashlight on the corpse, feeling extremely frightened. After his expression calmed down, he carefully observed the female corpse and thought, "What a beautiful figure!" ”

This female corpse swimsuit has distinct traces, full breasts, and a white and delicate lower abdomen, giving people a strong sense of intuition. Her legs were spread apart, and she must have been raped.

7

Tian Chunda, head of the city's criminal investigation detachment, quickly remembered the murder that had occurred a week earlier after observing the corpse. Because the victim's tanned skin and white marks on his bikini were too similar to that case, even more so than the strangulation marks.

"The criminals are so hateful!"

Hao Dong, the criminal policeman who came with him, said angrily.

The pain of the neck distorted the victim's face: the tongue was outstretched and the teeth were bared; The eyeballs are rounded and protruding from the orbits. One side of the ground was littered with clothes and shoulder bags that had been taken off. Hao Dong immediately checked the contents of the backpack. Found in cosmetics, handkerchiefs, and pocket money bags the commuter ticket holder, which contained the student commuter pass. The victim's name is Gu Qing, 20 years old; She is a third-year student in the English Department at Nanshan University, and her address is an apartment at a nearby school.

In order to identify the victim, the criminal police immediately called the management of the school apartment. During this time in the Administrator's future, the medical examiner performed an autopsy. The members of the investigation team were busy taking pictures at the scene. The killer may have been wearing gloves and no fingerprints were found at the scene. Only a dagger was found on the ground. The victim's briefs were cut by a knife, and it may have been cut with a dagger because the murderer was in trouble to take them off.

The apartment administrator rushed to the scene with a pale face. He confirmed that the deceased was Gu Qing himself. "Her family runs a big shopping mall. The family remits tens of thousands of yuan every month. The administrator added.

After listening to the administrator's narration, Tian Chunda thought in her heart that if she had such a sum of money every month, she should live a fairly wealthy student life, but she only had change in her purse, and it must have been the murderer who stole the wallet.

The autopsy report was delivered the following afternoon. The cause of death was determined to be strangulation, and the presumed time of death was between 10 and 11 p.m. on the 12th.

The victim was indeed raped. The blood of the murderer is identified as type B from the semen remaining in the vaginal passage. It's similar to the case in a suburban park.

The detectives studied the case together.

"Let's confirm what these two cases have in common?"

Tian Chunda said facing the blackboard. This seems to allow the image of the murderer to emerge.

"The first is the murderer's blood type."

Hao Dong said.

"Murderer's blood type B."

Tian Chunda wrote these words on the blackboard.

"Both cases happened on Friday." The detective said to the ocean.

"I've noticed that, too." Tian Chunda said: "Let's call this murderer 'Black Friday'. Maybe Friday has some meaning. Anything else? ”

"And ......," Hao Dong said, "in both cases, the murderers stripped the victims of their clothes. Another recent case of rape and murder, in which the killer only exposed the lower half of the victim's body, was completely different from these two cases. ”

"Do you think this reveals the character of the murderer?"

Tian Chunda asked with interest.

"It's not necessarily true, but it's worth noting. In the first case, perhaps as Meng Xiaochun said, the murderer wanted to rob and take off the watch after killing someone, but because it was a woman's watch, he was afraid of being traced and threw it away. There seems to be no intention of murder and robbery. I think the murderer's motive was to make the woman completely and completely naked. Hao Dong replied.

"Why did the murderer do that?"

Tian Chunda asked.

"I don't know."

Hao Dong replied honestly.