Putting down the enamel jar in his hand in a daze, Lao Bai looked confused: "I went to see Peking Opera yesterday afternoon, and I forgot about the stubble......

Liu Guodong: "......"

Although Liu Guodong did not speak, there was some resentment in his eyes.

Have we touched the fish to this extent?

Lu Chuan blinked and said suspiciously, "...... Master, what's the matter? ”

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

"The economic investigation detachment sent it over, and asked us to help identify fingerprints, but asked not to destroy the envelope."

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

Because the criminal investigation side has its own on-site investigation and trace inspection equipment, it can do the technical appraisal in recent years.

But the economic investigation side is different, they themselves do not have the talent in this area, and they do not have the equipment.

The evidence found in the handling of the case needs to be sent to the technical appraisal center according to the process.

It should not be sent in for criminal investigation.

"It has been sent, but what level is the technical appraisal center of the city bureau, it is difficult to extract fingerprints on the paper, not to mention the kraft paper envelope of coarse fiber."

Liu Guodong had already put on his gloves, picked up the envelope and observed it in the sun: "They can't do it over there, so the investigators have begged us." ”

Lu Chuan nodded, but with his understanding of Liu Guodong, Lao Bai and Yang Sen's strength, he extracted fingerprints from the paper without loss......

"Master, extract fingerprints from lossless paper...... It's difficult. ”

Liu Guodong snorted and put down the envelope: "It's not just difficult, extracting fingerprints from paper is a big problem. ”

To extract fingerprints, the easiest thing to do is 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, and in the later fingerprint comparison, the time spent is less, and the probability of successful comparison is high.

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

This is the case with carriers such as wood, fur, etc.

Paper is the most representative of them all.

Because the paper is made up of plant fibers, which are not visible 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 done with ordinary iodine fumigation.

The principle of this method is that the sweat of the fingerprint contains crystals of sodium, and a chemical reaction occurs after iodine fumigation.

Thus developing the fingerprint.

But this method has a drawback, and that is that it destroys the fingerprint.

In other words, the chemicals left behind by the fingerprint are only capable of a chemical reaction once.

After that, the fingerprints will disappear and there will be marks on the paper.

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

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

"Lao Liu, the gang of dry food in the technical appraisal center, if you can't get it yourself, let the economic investigation find us."

Bai Wenhai was obviously a little emotional: "Let's just reply that it won't work." ”

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

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

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

In the arson case in the southern suburbs and the sinking of corpses in the reservoir, Lu Chuan was very good at collecting fingerprints from fires and floods.

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

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

Or rather, there is no benefit.

After a while, Liu Guodong looked at Lu Chuan: "Xiao Lu, do you have a way?" ”

Lu Chuan did not hesitate: "There is a way, but we don't have relevant equipment, and with ordinary methods, if you want to extract fingerprints losslessly, you basically can't do it." ”

Liu Guodong listened to it, and his eyes lit up.

"What's the solution?"

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

Well?

"What is this?"

Lao Bai obviously hadn't heard of this thing.

"In recent years, the popular lasers to collect biological samples are all fixed-wavelength lasers."

Liu Guodong and Lao Bai nodded, they had heard of this thing, but they had never seen it.

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

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

"But fingerprints on paper, with this fixed-wavelength laser to collect biological samples, the fingerprint cannot be developed on the paper."

"You need to adjust the band."

Lu Chuan didn't say what the frequency of the specific adjustment was, anyway, there was no instrument, and it was useless to say it.

"Is there any other way besides this method?"

Lu Chuan shook his head: "Definitely not, other methods will destroy fingerprints and leave traces, only the method I said." ”

"The instrument...... How much? ”

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

Who doesn't know that the economic investigation detachment is very rich.

If nothing else, look at the car that people configure.

BBA is available in full sets, even at the high-end level.

What about the criminal investigation detachment?

There are only two Cruisers, one of which is ten years ago.

The reason why the investigation requested non-destructive fingerprint extraction 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 returned.

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

So......

It's a rip-off...... No, it's a good opportunity to deepen the friendship between criminal investigation and economic investigation.

"More than 400,000 yuan, this thing is quite widely used, and we have it sold in Haizhou City."

Lu Chuan actually didn't know how much it was, but he used it in the Tianzhou City Criminal Investigation Detachment the day before yesterday.

I asked Li Kai about the equipment.

"More than 400,000 ......"

Not a big problem.

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

Three hours later, just before I got off work at noon.

Liu Guodong rushed back in the dust.

At the same time, he was accompanied by a variable frequency laser spectrum analyzer.

"Master...... This is? ”

Lu Chuan didn't expect that Liu Guodong went out for a trip and really got this thing back.

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

Gee.

Lao Bai circled around the instrument for half a circle, and his mouth was full of words: "The investigation is rich, more than 400,000 yuan, and it can be approved so quickly!" ”

Liu Guodong agreed with Lao Bai's words: "They have 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!"