Coroner Ke Xue

Hearing Lin Xinyi's sigh, Asai Narumi couldn't help but feel entangled——

Indeed, so far, the only evidence found at the scene is:

A splotch of saliva on a cardboard box, shooting residue on an exterior wall, a clear umbrella with no fingerprints.

The shooting residue and umbrella can prove that the utility room on the 9th floor was the crime scene where the murderer opened fire.

The saliva stains can prove that Matsuo Takashi has been here.

But adding these two points together, it cannot be deduced that Matsuo Takashi was the murderer who shot Suwa in the utility room.

After all, "Matsuo was here" does not mean "Matsuo was here at the time of the crime."

Matsuo Takashi could say that he had been here in the past two days and accidentally sneezed, leaving traces.

"so what should I do now?"

Asai Chengmi frowned slightly and asked Lin Xinyi.

But Lin Xinyi spread his hands helplessly:

"There are many ways, but it all depends on luck."

"We look forward to finding more evidence elsewhere in the building, such as the gloves hidden by the murderer."

"Or, we hope that the search section will be able to show off its power and find out how Matsuo purchased the firearm, proving that the gun belongs to Matsuo."

"Or, based on the existing evidence, Matsuo is suspected of committing a major crime, and takes him back for interrogation as a suspect. Then use interrogation psychology to break through his psychological defenses bit by bit."

In actual case detection, not every case is so easy to find strong evidence and can be solved entirely by trace examination and forensics.

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

only.

In reality, it was Lin Xinyi's capable criminal police colleagues who were responsible for investigation and interrogation.

But now, his teammates are searching for a lesson.

Thinking of this, Lin Xinyi suddenly lost confidence:

“Let’s try again”

"Can you find stronger evidence?"

"Yeah" Asai Naomi responded absently.

Then, after some deep thought, he couldn't help but asked Lin Xinyi:

"Mr. Lin Xinyi."

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

"Is there any scientific method that can determine the exact time when the saliva stains were left?"

Hearing this, Lin Xinyi was slightly startled.

He understood Asai Narumi’s intention in raising this question:

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

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

As long as the exact time when the saliva stains are left can be determined,

This can further determine when exactly Matsuo came to this utility room.

If this time coincides with the time of the crime, then the combined evidence will be enough to send him to court for trial.

"Determining the exact age of salivary spots."

Lin Xinyi thought carefully along this line of thought, and finally gave a disappointing answer:

"Yes, I can—"

"Because the concentrations of urea and amino acids in salivary plaques change non-linearly with time."

"So as long as the concentration ratio of urea and amino acids in salivary spots is measured and substituted into the regression equation, the remaining time of salivary spots can be calculated."

"However, the minimum time that saliva stains are left behind determined by this method can only be accurate to 'days'."

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

There is no way to solve this case just by being accurate to the 'day'.

The time when the saliva stains were left behind must be accurate to the 'hour' in order to prove that Matsuo came to this utility room during the three-minute break at 10 o'clock.

"Is this idea really unworkable?"

"There is no one way."

"Can you estimate the time the saliva stains were left to the nearest hour or even minutes?"

Facing the dilemma set by the murderer, Asai Chengmi fell into deep thought.

And in this fog.

The unique perspective brought by his career as a doctor suddenly allowed him to see a direction:

"Matsuo Takashi. You have the flu, right?"

"Yes." Lin Xinyi was a little confused.

"What time is it now?"

"10:50."

"That's good. There is still hope."

A charming smile appeared on the corner of Asai Narumi's mouth, and the ponytail on the back of her head swayed excitedly:

"First extract the saliva plaque."

"Then quickly find ice cubes, dry ice. The TV station should have dry ice used to create stage effects!"

"Use dry ice to freeze and preserve saliva stain samples!\

,""Why use dry ice?" Lin Xinyi asked curiously.

He had handled so many cases as a forensic doctor, and he had never seen this move before.

However, Asai Narumi replied with a mysterious face:

"Because dry ice can create low temperatures of more than minus 70 degrees, it can be used to preserve influenza viruses for a long time."

the other side.

Matsuo Takashi has taken the smoke test in the forensics class.

The result of the test was that there was no gun smoke reaction on his body.

The Forensic Division police officer responsible for examining the pistol also reported that no skin flakes or fingerprints were found on the pistol.

"hehe."

"I've already told you that I'm not a murderer, so don't accuse good people unjustly."

Faced with the test results that were absolutely beneficial to him, the anxious Matsuo Takashi felt relieved a little.

Matsuo Takashi was sarcastically mocking the police officers guarding him while thinking to himself:

He was wearing gloves when he committed the crime, and there should be no fingerprints on the umbrella. The call was made using an anonymous disposable mobile phone, and checking his call records was useless.

After killing the person, he threw the gloves into the bathroom toilet and flushed them away. The police probably would not have found them. The mobile phone was hidden in the toilet tank. Even if it was found, there would be no fingerprints on it for investigation.

In that case, then this time.

Even if the Metropolitan Police knew that he was the murderer, they probably wouldn't have enough evidence to convict him.

Hmm. As long as you don't let the police find out, just buy the gun yourself.

If the police could find this out and get the gun dealer to identify him, he might not be able to escape.

Matsuo Takashi felt relaxed for a while, and nervous for a while, waiting anxiously for Lin Xinyi's investigation results.

And just then.

Lin Xinyi finally arrived.

But this time the leader was not Lin Xinyi as the management officer, nor was it Mao Lilan who had just made a splash.

Instead, she is a beauty dressed in men's clothing with a heroic single ponytail.

"Oh, someone else is here to deal with me again?!"

Matsuo Takashi pretended to be disdainful, but at the same time he carefully looked at the beautiful girl who took the lead:

Hmm. I can’t tell you about my strength, but my looks are pretty good.

I have to say that Manager Lin really enjoys it.

The two assistants beside him are both young girls whose appearance is not inferior to that of idol stars.

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

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

Narumi Asai, who appeared first, did not answer.

He just suddenly asked head-on without thinking:

"Mr. Matsuo."

"Did you accidentally sneeze in that utility room when you were shooting to kill someone?"

"Uh?" Matsuo Takashi was slightly startled.

He didn't know why the other party asked this question, but after he shot everyone, he couldn't help but sneeze in the utility room.

Suddenly being told the truth, he immediately looked away with a guilty conscience and said with a stern face:

"Say, what are you talking about?"

"I did go to that utility room and couldn't help but sneeze."

"But, that's all today, um, today's noon!"

"At night, especially those three minutes at 10 o'clock, I have never been to that place!"

Matsuo Takashi defended in a stern tone.

As soon as Asai Narumi saw his slightly guilty expression, he breathed a long sigh of relief:

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

"This way, I feel relieved."

"What do you mean?" Matsuo Takashi faintly heard something bad.

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

This is exactly what Mao Lilan took out before, the evidence bag containing the blood-stained mobile phone next to the deceased's body.

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

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

"Yeah." The onlookers nodded subconsciously.

Asai Narumi continued:

"Mr. Lin taught me that splatter-like blood stains are only formed when the blood in the body is ejected due to blood pressure when the deceased was injured before death."

"The closer the subject is to the wound, the denser the spattered blood droplets are distributed."

"And the presence of such densely distributed spatter-like blood stains on the mobile phone shows..."

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

"What does that mean?!"

Matsuo Takashi still didn't understand what evidence the other party had found, and he became increasingly panicked.

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

Asai Narumi said calmly:

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

"So we can confirm that Mr. Suwa was shot to death from upstairs with a gun at around 10:02."

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

"This shows that the specific location where the murderer shot was the utility room on the ninth floor."

After saying this, he concluded:

"According to this, the time of the crime was determined to be around 10:02."

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

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

"Not here!"

Matsuo said with an ugly expression:

"I told you, I didn't go there at all at night."

"I just went to the utility room once at noon to have a cigarette."

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

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

He mustered up the courage to defend himself thus.

But Narumi Asai gave him a confident smile:

"sure!"

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

"Then the saliva stains you left behind will also contain the influenza virus in your body!"

"W-what?" Matsuo Takashi was confused when he heard this: "Flu. Virus?"

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

"It's simple-"

"Detection of Influenza Virus Activity."

Asai Narumi paused slightly and said slowly:

"Viruses need living cells as vectors to survive."

"Generally, when viruses are exposed to dry air, due to water loss, temperature changes and many other factors, the protein quickly loses its original structure, and even the entire envelope shell breaks into fragments."

"The influenza virus has weak external resistance and is quite sensitive to heat."

"Although the TV station building has central air conditioning, the window in the utility room is always open, and the hot air from outside flows in, making the temperature relatively high."

"Based on the temperature in that utility room, even the most survivable influenza A virus can only remain active for 2 hours after the influenza virus leaves the human body."

"This" Matsuo Takashi's expression changed.

After 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, conversely, if active influenza virus can still be detected in saliva spots"

Asai Narumi gave the answer:

"That means you have been to that utility room in the past two hours!"

"Mr. Matsuo, according to my interview, you started preparing for the evening program with the program team at 4 p.m."

"We will receive Mr. Lin and Miss Maori at 7 o'clock, and then stay with them for 2 hours."

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

"In other words, within the seven hours from 4 p.m. to now."

"The only time you can go to the utility room out of everyone's sight-"

"Only those 3 minutes at 10 o'clock when the live show takes a break!"

As long as the active virus can be detected in the saliva spots, it means that Matsuo has been to the utility room in the past two hours.

During this period, even going back to 4 p.m., the only time he had time to go to the utility room was for those three minutes.

"That being the case, it's easy to conclude—"

"As long as active influenza virus can be detected in saliva spots, it means"

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

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

There was a different kind of brilliance in Asai Narumi's eyes.

Speaking of which, this was his first time participating 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.

Transforming from a vengeful demon to a righteous enforcer is an amazing feeling.

If I had to describe it, it would be a kind of light like a new life.

"Now I have preserved the saliva stain samples in the utility room with dry ice and sent them to Mihua Hospital for virus testing."

"So, Mr. Matsuo"

"Let us look forward to the test results of virus activity together!"

Asai Narumi looked at Matsuo with bright eyes.

As for Matsuo Takashi, his face was already ashen.