The tape paper extraction method is suitable for the extraction of dust handprints on the surface of smooth objects.

In the case where the contrast between the dust handprint and the object is not obvious, the influence of the object can be avoided by using adhesive tape.

At Lin Xinyi's request, the servant of the Sewa family quickly sent a roll of wide tape.

The Seba family has a big business, and the utility room is wider than the living room of an ordinary person's house, so this kind of daily sundries are always ready.

So, in the nervous gaze of Old Man Seba...

Lin Xin began to use his family's tape to extract the handprints he had left behind.

And the extraction process is also very simple...

The principle and operation are probably similar to that of elementary school students using tape paper to glue typos on their workbooks.

Spread the wide tape evenly over the glass, press it hard, and then carefully tear it off.

The dust-formed handprint was neatly glued to the wide tape.

"But... Still a little hard to see? ”

The officers asked concernedly.

Although the handprint is easy to hold on tape paper, it is still a little unclear.

"It's okay, have you forgotten the operation you just made to find the handprint?"

"We can also use this method of light transmission enhancement, and it's much more convenient to operate."

As he spoke, Lin Xinyi gently placed the wide tape with handprints in front of the black body of the TV in this guest room.

The background color is changed, and the contrast is more obvious.

The handprints on the tape paper suddenly became much clearer.

"Here, flashlight, light from the side at a 45-degree angle."

Lin Xinyi continued to guide several rookie operations:

And this time, as soon as the lights were turned on, the dust handprints on the wide tape were more clearly visible against the black background.

Because of the particle nature of dust, dust handprints are opaque and diffusely reflective, while the tape that sticks to dust handprints has better light transmittance.

Therefore, when the light source is illuminated at an angle of 45 degrees, the part of the tape with dust attached to it is diffuse under the irradiation of the light, and the part of the tape without dust is specular under the irradiation of the light, which enhances the contrast of the handprint.

"Now you can see it clearly!" The officers of the forensic division shouted excitedly.

"Take a photograph of the record." Lin Xinyi's tone was calm, and he ordered them to do the only thing they were good at.

In this way, the officers of the forensic division took pictures of the handprints, and the wide tape with the handprints was well preserved.

"It's... This..."

Sewa Sontoku's face changed slightly, and then he asked calmly:

"With this handprint, you can catch the prisoner, right?"

"It can make a big difference."

"Because of differences in age, gender, weight, bones, etc., the contours of each person's hand will be slightly different."

"Although there is no palm print to accurately lock the identity, by comparing the contours of the hand, at least the scope of the investigation can be greatly narrowed."

Lin Xinyi cautiously explained with these words.

"Oh... It's just narrowing it down..."

Old Mr. Seba's battered heart was a little respite.

But he didn't expect that Lin Xinyi was like the landlord master with 17 cards in his hand, although he had thrown out the bomb, but the good cards in his hand were far from finished:

"It's still a bit reluctant to rely on handprints to find the murderer."

"So I'll use another method, which can extract the murderer's footprints as well."

"Footprints?"

Several officers of the forensic division asked curiously:

"Can you still find and extract footprints with wide tape?"

"No, you can't use duct tape this time." Lin Xinyi shook his head slightly:

The adhesive tape is so adhesive that it can absorb almost all the dust on the surface of the object.

And the glass window was cleaned by the servants every day, and it was clean and clean, without any dust.

All dust handprints can be extracted directly from the glass with adhesive tape without being disturbed by other dust.

But the footprint is different.

Footprints may be on the floor, on the walls, and on the marble handrails...

Those areas are coarser than the glass and covered with more dust.

If you use a highly adhesive tape directly, I am afraid that you will only end up with a piece of tape covered with dust.

Therefore, if you want to extract footprints, you must use a more high-tech method.

"That..."

Lin Xinyi looked around in the guest room.

Finally, he stared at the boxy old-fashioned TV again:

"Tear down this TV, remove the black chassis panel on the side of the TV."

"Huh?" None of the officers reacted:

Why dismantle someone's TV, which can also be used to solve crimes?

"Directly dismantle!"

"Demolished me... Forehead... The Twilight Police Department will pay for it! ”

Lin Xinyi urged without explanation.

So, several young police officers immediately dismantled the TV with quick movements.

Sewa wanted to stop it, but he couldn't open his mouth - as a chaebol boss, he couldn't even give up a TV.

Soon, the TV was disemboweled.

The flat and wide black fuselage side panels were also carefully removed by the police.

"And then?"

Looking at this big black plastic plate, everyone was puzzled.

But Lin Xinyi pointed to the plastic plate that had just been removed from the TV and instructed the policemen:

"You take a couple of clothes and other textiles and rub them against this plastic plate."

"Friction?" The officers were slightly stunned.

"Rub!"

Lin Xinyi felt like he was teaching elementary school students.

And think about it... Ha, light, plus tape... He seems to be teaching things that elementary school students do.

Even, even the trick used now is also within the scope of primary school students' knowledge:

"Triboelectric electricity, understand?"

"Rubbing the plastic sheet to make it electrostatic, and then spreading the electrostatic plastic sheet to a place where there may be a dust footprint."

As a forensic doctor, Lin Xinyi will always go to the scene with his trace examination colleagues who are also technical investigators.

And the equipment they use most to extract dust footprints is the electrostatic adsorber.

Now there is no ready-made electrostatic adsorber, Lin Xinyi can only try, let these police officers use soil methods, soil materials, and human friction to create electrostatic adsorption devices.

"When a tiny non-statically charged object is close to an electrostatic object, due to the electrostatic induction phenomenon, the end close to the electrostatic object will induce the opposite electrical properties to the electrostatic object, which in turn will cause the tiny object to be attracted and attached to the electrostatic object."

Lin Xinyi briefly explained the principle of electrostatic adsorption:

"So as long as the electrostatic plastic plate is spread in a place where there may be a dust footprint, the dust on the object will be adsorbed to the plastic plate due to the electrostatic adsorption effect."

"The dust on the object is transferred to the black plastic plate, and because the background color difference is strengthened, the dust footprints that are difficult to distinguish with the naked eye can be relatively clearly visible."

He explained at length.

I don't know if the police officers understood, but they were busy anyway.

In front of this black plastic plate, several young men took off their coats and rubbed hard, and after a while, the board was about to burn.

Then, according to Lin Xinyi's instructions, they tried to spread the plastic sheet that had been statically charged to the railing of the balcony.

The handrails are made of marble and have a wide upper edge, which is perfect for climbing with your feet.

Therefore, Lin Xinyi regarded it as the primary suspect of possible footprints.

And the results were not unexpected.

The officers spread the black plastic plate on the marble handrail, waited for a moment and then picked it up...

An almost complete dust shoe print had clearly appeared on the black plastic plate.

"It's over!"

Seeing this, Sewa Sontoku's face turned green:

The previous handprint only made him feel dangerous, but now this shoe print is a real damn thing!

Because his left foot is still wearing the shoes of that time!

At that time, he was in a hurry to show up in front of everyone, and there was a murder in the house, and the servants would definitely come to his room to find him soon...

Therefore, his solitary activity time after committing the crime was very short.

In such a short period of time, Sewa had to jump from the balcony to the opposite wall with a rope, climb back to his room, hide gloves and masks, change into clean clothes, and re-wrap his right leg in a plaster.

It's really hard for him to do so many things in 2 or 3 minutes.

As soon as the time became tense, Sewa Sonde didn't care about changing the most inconspicuous shoes-

After all, he deliberately looked at it when he left the scene, and he didn't leave any shoe prints.

But I never expected...

Lin Xinyi actually used a trick of elementary school-level knowledge to find out the shoe prints that he couldn't see with the naked eye!

Thinking of this, Sewa Sontoku's heart was already pounding.

He could only pray, praying that Lin Xinyi would let him go, a "disabled person", and not come to him with that handprint and footprints.

But at this moment...

"The handprints and footprints have been found."

"So... Mr. Sentoku Seba, you will be the first to compare! ”

Lin Xinyi turned around and glanced at Sewa Zunde in the wheelchair.

"W-What?!"

Old Man Seba's face was completely bloodless:

"Why are you looking for me..."

He pretended to be disabled, why could Lin Xinyi still be the first to think of him?!

Don't... Was your disguise discovered from the beginning?

And Lin Xinyi's answer was:

"Because you're talking too much."

"And... I was ridiculed by you just now, and I'm still quite upset. ”