Putting down the enamel jar in his hand blankly, Lao Bai looked confused: "I went to see the Peking Opera yesterday afternoon, and I forgot about that..."
Liu Guodong: "..."
Although Liu Guodong didn't speak, there was some resentment in his eyes.
Have we fished to this extent?
Lu Chuan blinked and asked in confusion: "...Master, what's the matter?"
Two minutes later, a letter was placed in front of Lu Chuan.
"The Economic Investigation Detachment sent it over and asked us to help identify the fingerprints, but we were asked not to damage the envelope."
"Why didn't they send the stuff 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 appraisals in recent years by itself.
But the economic investigation side is different. They don’t have the talent or equipment in this area.
The evidence discovered during case handling needs to be sent to the technical appraisal center according to the process.
It shouldn't have been sent to criminal investigation.
"It has been sent, but what is the level of the technical appraisal center of the municipal bureau? It is difficult to extract fingerprints from paper, not to mention it is a thick fiber kraft paper envelope."
Liu Guodong had already put on his gloves, picked up the envelope and looked at the sunshine: "They can't do it over there, so the economic investigation people asked us."
Lu Chuan nodded, but based on his understanding of Liu Guodong, Lao Bai and Yang Sen's abilities, fingerprints could be extracted without damaging the paper...
"Master, it's difficult to extract fingerprints from non-destructive paper..."
Liu Guodong snorted and put down the envelope: "Not only is it difficult, extracting fingerprints from paper is already a moderate problem."
The easiest way to extract fingerprints is on a dry surface with a smooth surface and no water absorption.
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, less time is spent and the probability of successful comparison is high.
However, it is very difficult to extract fingerprints from some carriers with rough surfaces and water-absorbent surfaces.
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, which are invisible to the naked eye, there are actually large gaps between the fibers and extremely poor flatness.
The sweat stains and grease left by fingerprints on the paper will be quickly absorbed by the paper.
Generally speaking, fingerprint extraction on paper can be completed using ordinary iodine fumigation method.
The principle of this method is that the fingerprint sweat contains sodium crystals, and a chemical reaction will occur after iodine fumigation.
This develops the fingerprint.
But this method has a disadvantage, which is that it will destroy the fingerprint.
In other words, the chemical substances remaining in the fingerprint can only undergo one chemical reaction.
The fingerprints will then disappear and traces will remain on the paper.
The difficulty of this mission is that the economic investigation requires that no traces be left and fingerprints must be extracted without damage.
Then, neither iodine fumigation nor ice sampling methods will work.
"Old Liu, those people in the Technical Appraisal Center who are doing nothing can ask the economic investigation to find us if they can't do it themselves."
Bai Wenhai was obviously a little emotional: "Why don't we just reply and say no, forget 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. Lu Chuan is in the current survey office.
Lu Chuan was very good at collecting fire fingerprints and water immersion fingerprints in the arson cases in the southern suburbs and the corpse sinking cases in the reservoir.
This shows that Lu Chuan's ability in fingerprint collection should far exceed that of the three of them.
The question is, will there be any subsequent trouble after this help?
In other words, are there any benefits?
After a while, Liu Guodong looked at Lu Chuan: "Xiao Lu, is there anything you can do?"
Lu Chuan did not hesitate: "There are ways, but we don't have the relevant equipment, and it is basically impossible to extract fingerprints losslessly using ordinary methods."
Liu Guodong's eyes lit up after hearing this.
"any solution?"
Lao Bai also came over and listened to Lu Chuan's words: "Variable frequency laser spectrum analyzer."
Um?
"What the hell is this?"
Lao Bai has obviously never heard of this thing.
"The lasers that have become popular in collecting biological samples in recent years are all lasers with fixed wavelengths."
Liu Guodong and Lao Bai nodded. They had heard of this thing but had never seen it before.
I heard that this laser-based instrument for collecting biological samples has a good detection effect on human teeth, bones, blood, sweat stains, semen spots, saliva, etc.
However, this thing is too expensive, and the Haizhou City Criminal Investigation Detachment does not have it.
"But for fingerprints on paper, the instrument that collects biological samples with this fixed-wavelength laser cannot develop fingerprints on paper."
"You need to adjust the band."
Lu Chuan did not say the specific frequency of adjustment. Anyway, there is no instrument, so it is useless to say it.
"Besides this method, is there any other way?"
Lu Chuan shook his head: "Definitely not. Other methods will destroy the fingerprints and leave traces. This is the only method I mentioned."
"The instrument...how much does it cost?"
When asking this question, Lao Liu's eyes were shining.
Who doesn’t know that the Economic Investigation Detachment is extremely rich?
If nothing else, look at the car they configured.
The whole set of BBA is available, even at the high-end level.
What about the criminal investigation detachment?
There are only two Cruisers, one of which is from ten years ago.
The reason why the economic investigation requested non-destructive fingerprint extraction this time was because the envelope had special markings.
It was originally obtained by special means to collect fingerprint evidence. If it is destroyed or traces are left, the envelope cannot be sent back.
The suspect will find that the envelope has been tampered with.
so……
This is a blackmail... No, it's a good opportunity to deepen the friendship between criminal investigation and economic investigation.
"More than 400,000 yuan. This thing has a wide range of uses. We sell it in Haizhou City."
Lu Chuan actually didn't know the exact amount of money, but he used it at the Tianzhou City Criminal Investigation Detachment the day before yesterday.
I asked Li Kai about the equipment.
"More than four hundred thousand..."
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 when I was about to get off work at noon.
Liu Guodong rushed back after a long journey.
At the same time, a variable frequency laser spectrum analyzer followed him back.
"Master...this is?"
Lu Chuan didn't expect that Liu Guodong would actually get this thing back after going out for a while.
"Haha, the economic investigation team sponsored it. Although it is not our asset, we helped them get fingerprint analysis. This thing is borrowed by our detachment for free!"
Tsk tsk.
Lao Bai circled the instrument half a circle and said, "Economic investigation is rich, more than 400,000 yuan, and it can be approved so quickly!"
Liu Guodong agreed with Lao Bai: "They encountered a big case over there, and this envelope is the key."
"Okay," Liu Guodong looked at Lu Chuan: "I'll leave the instrument and envelope to you."
"Waiting for your good news!"
"no problem!"
