Hearing Lin Xinyi's sigh, Asai Narumi couldn't help but fall into a tangle-

Indeed, at present, the only evidence found at the scene is:

Saliva spots on cardboard boxes, shooting residues on the outer wall, a transparent umbrella without fingerprints.

The shooting residue and umbrella can prove that the utility room on the 9th floor is the scene of the murderer's shooting.

Saliva spots prove that Takashi Matsuo has been here.

But these two points together cannot be deduced that Takashi Matsuo is the murderer who shot Suwa in this utility room.

After all, "Matsuo has been here" does not mean that "Matsuo has been here at the time of the crime".

Takashi Matsuo can say that he has been here for the past two days, and accidentally sneezed, so he left a trace.

"So what to do?"

Asai Chengshi frowned slightly and asked about Lin Xinyi.

But Lin Xinyi spread his hands helplessly:

"There are a lot of ways, but it all depends on some luck..."

"Expect to find more evidence elsewhere in the building, such as the gloves that the killer hid."

"Or, I hope that the search lesson can be 'powerful' and find out how Matsuo purchased the firearm, and prove that the gun belongs to Matsuo."

Or, with the available evidence proving that Matsuo is suspected of committing a major crime, take him back for interrogation as a suspect. Then use the psychology of interrogation to break through his psychological defenses little by little. ”

In the actual investigation of a case, it is not so easy to find strong evidence in every case, and it can be solved completely by relying on trace examination and forensic medicine.

It is often the technical investigation that cooperates with the investigation and interrogation, and the division of labor and cooperation between the two complement each other, so as to form a complete chain of evidence and bring the murderer to justice.

Merely...

In reality, it is Lin Xinyi's powerful criminal police colleagues who are responsible for the investigation and interrogation.

But now, his teammates, is a search lesson.

Thinking of this, Lin Xinyi suddenly lost confidence:

"Let's try again..."

"Can you find stronger evidence?"

"Hmm..."Asai Nari replied absentmindedly.

Immediately afterwards, after some contemplation, he couldn't help but ask Lin Xinyi a question:

"Mr. Lin Xinyi."

"Since the saliva spots can prove that Matsuo has been here."

"Is there any scientific method... Can you determine the saliva spots, the exact time of remaining? ”

Hearing this, Lin Xinyi was slightly stunned.

He understands Asai's intention in asking this question:

At present, the time of death of the deceased is certain, and the scene of the murderer's crime can also be proven.

Then, as long as it is proved that Matsuo appeared at the scene of the crime at the time of the crime, he can be more strongly identified as the murderer.

And as long as the exact age of saliva spots can be determined....

It can be further determined when Matsuo came to this utility room.

If this time coincides with the time of the crime, then the sum of this evidence is enough to send him to court for trial.

"Determine the exact time of saliva plaque..."

Lin Xinyi thought carefully along this line of thought, but in the end, he gave a disappointing answer:

"Yes, yes—"

"Because the concentration of urea and amino acids in the saliva plaque will change nonlinearly with the time of retention."

"Therefore, as long as the concentration ratio of urea to amino acids in the saliva spots is measured and substituted into the regression equation, the residual time of the saliva spots can be calculated."

"However, the retention time of saliva spots determined by this method can only be accurate to 'days' at the very least."

Hearing this, Asai Narumi also understood what Lin Shinichi meant:

Just accurate to the 'day', there is no way to solve this case.

The time of saliva spots had to be accurate to the 'hour' to prove that Matsuo had come to the utility room during the three-minute break at 10 o'clock.

"Is this idea really not working?"

"There's no way..."

"Can you accurately determine the time left over for saliva spots to 'hours' or even 'minutes'?"

Faced with the dilemma set by the murderer, Asai Narumi fell into deep thought.

And right in the middle of this fog...

The unique perspective of his profession as a doctor suddenly gave him a direction:

"Takashi Matsuo... It's the flu, right? ”

"That's right." Lin Xinyi was a little puzzled.

"What time is it?"

"10:50."

"That's good... There is hope. ”

A touching smile appeared at the corner of Asai Narumi's mouth, and the ponytail on the back of his head shook excitedly:

"Extract the saliva spots first."

"Then hurry up and find the ice... No, dry ice, TV stations should have dry ice for stage effects! ”

"Use dry ice to freeze the saliva spot sample!" 、

"Why dry ice?" Lin Xinyi asked curiously.

He really hadn't seen this trick before.

But Asai Narumi replied with a mysterious face:

"Because dry ice can create a low temperature of more than minus 70 degrees, it is used to store the flu virus for a long time."

................................................

The other side.

Takashi Matsuo has already undergone a smoke test in the forensic class.

As a result of the test, there was no detectable gunsmoke reaction on him.

The police officer of the Identification Bureau who was in charge of examining the pistol also received information that no dander or fingerprints were found on the pistol.

"Huh."

"It's said that I'm not a murderer, don't wronged good people."

Faced with the test results that were absolutely favorable to him, the apprehensive Matsuo Takashi relaxed a little.

Takashi Matsuo mocked the police officers who were guarding him with a fierce and inwardly look, and thought to himself:

He was wearing gloves when committing the crime, and there should be no fingerprints on the umbrella.

After the killing, the gloves were flushed away by him in the toilet bowl of the bathroom, and they should not be found by the police.

In that case, this time...

Even if the Metropolitan Police Department knew that he was the murderer, I am afraid that there would not be enough evidence to convict him.

Well... As long as you don't let the police find out, it's good to buy your own guns.

If the police could find out about this and ask the gun dealer to identify him, he probably wouldn't have been able to escape.

Matsuo Takashi was relaxed for a while, and nervous for a while, so anxiously waiting for the results of Lin Shinichi's investigation.

And at this moment...

Lin Xinyi is finally here.

But this time it was not Lin Xinyi, who was the manager, nor Mao Lilan, who had just been in the limelight.

It's a men's beauty with a heroic single ponytail.

"Heh... Someone else to deal with me again?! ”

Takashi Matsuo was disdainful on the surface, but at the same time carefully looked at the beautiful girl who took the lead:

Well... I can't see the strength, but the appearance is very good.

I have to say that Managing Officer Lin will really enjoy it.

The two assistants around him are all young girls whose looks are not inferior to idol stars.

Matsuo Takashi maliciously speculated in his heart about Lin Xinyi's intentions, and then asked with a smile:

"What, have you found evidence that I'm the murderer?"

Narumi Asai, who led the reality, did not answer.

He just suddenly had no head and no brain, and asked on the spot:

"Mr. Matsuo."

"When you shot and killed, did you accidentally sneeze in that utility room?"

"Huh?" Matsuo Takashi was slightly stunned.

He didn't know why he was asking this question, but he couldn't help but sneeze in the utility room after shooting someone.

Suddenly told the truth, he immediately looked away with some weakness, and said with a calm face:

"Say what..."

"I've been to the utility room and... I couldn't help but sneeze. ”

"But that's all today... Well, it's noon today! ”

"At night, especially for the three minutes at 10 o'clock, I haven't been to that place at all!"

Takashi Matsuo defended himself with such a fierce expression.

And as soon as Asai Narumi saw his slightly weak performance, he breathed a long sigh of relief:

"It seems that those saliva spots were indeed left by you when you committed the crime."

"That way, I'm relieved."

"What do you mean..."Takashi Matsuo faintly heard a bad taste.

Narumi Asai did not rush to answer, but took out a transparent evidence bag.

This is exactly what Maolilan had taken out before, the evidence bag containing the bloodstained mobile phone next to the deceased's body.

"Let's take a look at this phone first..."

"Everyone can see the blood splatters on the phone, right?"

"Hmm." The onlookers all nodded subconsciously.

And Asai Narumi continued:

"Mr. Lin taught me that splattery blood stains are blood stains that can only be formed when the deceased was injured before his death, and the blood in his body was sprayed out due to blood pressure."

"The closer the subject is to the wound, the denser the splattered blood droplets become."

"And this densely distributed splattery of blood on the phone means that..."

"When the deceased was shot in the head, this mobile phone was next to the deceased's head."

"What does that mean?!"

Matsuo Takashi still didn't understand what evidence the other party had found, and his heart became more and more panicked.

"It can be said that at the moment when the deceased was shot, the cell phone was next to his head - he was making a call on the cell!"

Asai Narumi said unhurriedly:

"In that case, the last call time on the phone is the exact time of his death!"

"So we can be sure that Mr. Suwa was shot and killed from the upper floor with a gun at around 10:02."

"And just now, Miss Maori extracted the shooting residue from the window wall of the utility room on the 9th floor, which can detect the gunsmoke reaction."

"This shows that the specific place where the murderer fired the gun is the utility room on the 9th floor."

With that said, he concluded:

"Based on this, the time of the crime is determined to be around 10:02."

"The scene of the crime was determined to be the utility room on the 9th floor."

"So, Mr. Matsuo, around 10:02, are you in the utility room on the 9th floor?"

"Not here!"

Matsuo said with an ugly face:

"I said, I haven't been there at all at night."

"I just went to the utility room once at noon and went there to smoke a cigarette."

"Even if you can find any traces of me in the utility room..."

"There's no way to prove it, I went to the utility room at 10:02, right?!"

He plucked up the courage to defend himself in this way.

And Asai Narumi returned him a confident smile:

"Absolutely!"

"Mr. Matsuo, do you remember that you had the flu?"

"Then the saliva spots you left behind, there will also be flu viruses in your body!"

"W-What?" Takashi Matsuo was at a loss when he heard this: "The flu... Virus? ”

"How can the virus prove that I went to the utility room at 10:02?"

"It's simple—"

"Testing the activity of influenza viruses."

Asai Narumi paused slightly, and said slowly:

"Viruses need living cells as vectors to survive."

"Generally, viruses are exposed to dry air, and due to many factors such as water loss and temperature changes, the protein quickly loses its original structure, and even the entire envelope shell is broken and fragmented."

"The influenza virus, on the other hand, has weak external resistance and is quite sensitive to heat."

"Although the TV station building has central air conditioning, the utility room has always had the windows open, and the hot air from the outside poured in, and the temperature was relatively high."

"According to the temperature in the utility room, even the most survivable influenza A virus can only survive for 2 hours after the flu virus leaves the human body."

"This..."Takashi Matsuo's face changed.

Hearing this, he finally understood what the other party was talking about.

"If, as you said, the saliva spots were left by you in the utility room at noon, the virus in the saliva spots must have been inactivated by now."

"But, on the other hand, if there is still an active influenza virus detected in the saliva spots..."

Narumi Asai gave the answer:

"That means you've been to that utility room in the last two hours!"

"And Mr. Matsuo, as far as I know, you started preparing for the evening program with the program team at 4 o'clock in the afternoon."

"Received Mr. Lin and Miss Maori at 7 o'clock, and then stayed with them for 2 hours."

"The live broadcast started at 9 o'clock, ended the live broadcast at 10:20, and then went to the scene of the crime with everyone."

"That is, in the seven hours from 4 p.m. to now."

"The only time you'll be out of sight and go to the utility room—"

"It's only 10 o'clock, 3 minutes of break from the live show!"

As long as there is an active virus detected in the saliva spots, it means that Matsuo has been to the utility room in the last two hours.

And during this time, even going back to 4 o'clock in the afternoon, the only time he had time to go to the utility room was those 3 minutes.

"In that case, it's easy to conclude—"

"As long as an active influenza virus can be detected in the saliva spot, it means..."

"At around 10:02 a.m., you were in the utility room on the 9th floor that was the scene of the crime!"

"This point seriously contradicts your confession, which is enough to prove that you are the murderer!"

Asai Narumi's eyes shone with a different kind of brilliance.

Speaking of which, this is the first time he has participated in the investigation of a case as a police officer.

Not long ago, what he thought about every day was how to kill people in a more covert way.

It's a wonderful feeling to go from a vengeful demon to a righteous enforcer.

At the same time, it also made him feel a kind of light like a new life.

"Now the saliva spot sample has been stored by me with dry ice and sent to Rice Flower Hospital for virus testing."

"So, Mr. Matsuo..."

"Let's look forward to the results of the viral activity test!"

Narumi Asai looked at Matsuo with blazing eyes.

And Matsuo Takashi is already like ashes.