Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

Chapter 46

Putting down the enamel jar in his hand blankly, Lao Bai looked confused: "I went to see a Beijing opera yesterday afternoon, I forgot about that..."

Liu Guodong: "..."

Although Liu Guodong didn't speak, there was some resentment in his eyes.

Have we touched this level of fishing?

Lu Chuan blinked and asked in confusion, "...Master, what's the matter?"

Two minutes later, a letter was placed in front of Lu Chuan.

"It was sent over by the Economic Investigation Detachment. Please help us identify the fingerprints, but the envelope must not be damaged."

"Why didn't they send it to the technical appraisal center?"

Because the criminal investigation side has its own field survey and trace inspection equipment, it can do the technical appraisal in recent years by itself.

But the economic investigation side is different. They don't have the talents or equipment in this field.

Evidence found during the case handling needs to be sent to the Technical Appraisal Center according to the procedures.

Should not be sent for criminal investigation.

"It's already been delivered, but with the technical appraisal center of the Municipal Bureau, it's difficult to extract fingerprints from paper, let alone a coarse-fiber kraft paper envelope."

Liu Guodong had already put on his gloves, picked up the envelope and looked at the sun: "They couldn't do it over there, so the economic investigators asked us."

Lu Chuan nodded, but based on his understanding of Liu Guodong's old Bai and Yang Sen's strength, he can extract fingerprints without damaging paper...

"Master, extracting fingerprints from non-destructive paper...is it difficult?"

Liu Guodong snorted, and put down the envelope: "Not only is it difficult, but fingerprint extraction from paper is already a moderate problem."

Fingerprints are easiest to do on a dry surface with a smooth, non-absorbent surface.

For example, fingerprints on mobile phone screens, car door handles and other carriers are the least difficult to extract.

Moreover, the completeness of the extraction will be relatively high. In the later fingerprint comparison, it will take less time and the probability of successful comparison will be greater.

However, it is very difficult to extract fingerprints on some rough surfaces and water-absorbing carriers.

This is the case with carriers such as wood and fur.

Paper is the most representative of them.

Because paper is composed of plant fibers, this fiber is invisible to the naked eye, but in fact there are large gaps between the fibers, and the flatness is extremely poor.

The sweat and grease left by fingerprints on the paper will be quickly absorbed by the paper.

Generally speaking, fingerprint extraction on paper can be completed by ordinary iodine fumigation.

The principle of this method is that the sweat of fingerprints contains sodium crystals, and a chemical reaction will occur after iodine is smoked.

Fingerprints are thereby developed.

But this method has a disadvantage, that is, it will destroy the fingerprint.

That is to say, the chemical substance left by the fingerprint can only undergo a chemical reaction once.

Fingerprints will then disappear and marks will be left on the paper.

The difficulty of this mission is that the economic investigation side requires that no traces be left and fingerprints must be extracted without damage.

Then, neither the iodine fumigation nor the ice method will work.

"Old Liu, the gang in the Technical Appraisal Center have nothing to do, if they can't handle it themselves, let the economic investigation find us."

Bai Wenhai was obviously emotional: "Let's just reply that we can't do it."

Liu Guodong looked at the envelope and folded his arms in thought.

To be honest, if it was normal, he would refuse without even thinking about it.

But it's different now, there is Lu Chuan in the survey office.

In the arson case in the southern suburbs and the sinking corpse case in the reservoir, Lu Chuan was very good at collecting fingerprints from fire and water immersion.

This shows that Lu Chuan's strength in fingerprint collection should far exceed the three of him.

The question is, after this help, will there be any follow-up troubles.

Or rather, is there any benefit.

After a while, Liu Guodong looked at Lu Chuan: "Xiao Lu, is there anything you can do?"

Lu Chuan didn't hesitate: "There is a way, but we don't have the relevant equipment, and using ordinary methods, it is basically impossible to extract fingerprints without damage."

When Liu Guodong heard this, his eyes lit up.

"any solution?"

Lao Bai also came over and listened to Lu Chuan: "Frequency conversion laser spectrum analyzer."

Ok?
"What is this?"

Lao Bai obviously hadn't heard of this thing.

"The lasers that have become popular in recent years to collect biological samples are all fixed-wavelength lasers."

Liu Guodong and Lao Bai nodded. They had heard of this thing, but hadn't seen it.

I heard that this laser instrument for collecting biological samples has a good effect on human teeth, bones, blood, sweat stains, semen spots, saliva, etc.

However, the price of this thing is too expensive, and the Criminal Investigation Detachment of Haizhou City does not have this thing.

"But for fingerprints on paper, using this fixed-wavelength laser to collect biological samples cannot develop fingerprints on paper."

"Need to adjust the band."

Lu Chuan didn't say how often the adjustments should be made. Anyway, there are no instruments, so it's useless to talk about it.

"Aside from this method, is there any other way?"

Lu Chuan shook his head: "Of course not, other methods will destroy fingerprints and leave traces, only the method I mentioned."

"The instrument... How much is it?"

When asking this question, Lao Liu's eyes were shining.

Who doesn't know, the Economic Investigation Detachment is very rich.

Among other things, look at the car configured by others.

There is a full set of BBA, even high-end level.

What about the criminal investigation detachment?
Just two Cruisers, one of which was ten years ago.

The reason why the Economic Investigator requested non-destructive extraction of fingerprints this time was because the envelope had a special mark.

Originally, it was obtained by special means to collect fingerprint evidence, and if it was destroyed or left traces, the envelope could not be sent back.

The suspect will find that the envelope has been tampered with.

and so……

This is a scam... No, it's a good opportunity to deepen the friendship between criminal investigation and economic investigation.

"It's more than 40 yuan. This thing has a wide range of uses. We sell it in Haizhou City."

Lu Chuan actually didn't know the exact amount, but he used it at the Tianzhou Criminal Investigation Detachment the day before yesterday.

I asked Li Kai about the equipment.

"More than 40 million..."

The problem is not big.

Liu Guodong packed the letter and left the office directly: "Xiao Lu, wait for me in the office!"

Three hours later, when I was about to leave work at noon.

Liu Guodong rushed back in a hurry.

At the same time, a variable frequency laser spectrum analyzer followed him back.

"Master... this is?"

Lu Chuan didn't expect that Liu Guodong really got this thing back after going out for a while.

"Haha, the one sponsored by the economic investigation is not our property, but we help them do fingerprint analysis, and this thing is borrowed from our detachment for free!"

Gee.

Lao Bai circled the instrument for half a circle, tsk-tsk: "The economic investigation is rich, more than 40 yuan, and it can be approved so quickly!"

Liu Guodong agreed with Lao Bai's words: "They encountered a big case over there, and this envelope is the key."

"Okay," Liu Guodong looked at Lu Chuan: "The instrument and the envelope will be handed over to you."

"Waiting for your good news!"

"no problem!"

(End of this chapter)