Chapter 46 The Rich Economic Investigation
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 did not 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, asking us to help identify fingerprints, but the envelope must not be damaged."
"Why didn't they send the things to the Technical Identification Center?"< br>
Because the criminal investigation side has its own on-site investigation and trace inspection equipment, it has been able to 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.
Evidence discovered during case handling needs to be sent to the technical appraisal center according to the process.
It should not be 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 has already Putting on gloves, he picked up the envelope and looked at the sun and looked at it: "They can't do it over there, so the economic investigation people asked us."
Lu Chuan nodded, but based on his understanding of the abilities of Liu Guodong, Lao Bai and Yang Sen, extracting fingerprints with lossless paper...
"Master, extracting fingerprints with lossless paper... is difficult."
Liu Guodong He snorted and put down the envelope: "Not only is it difficult, extracting fingerprints from paper is inherently a moderate problem."
The easiest way to extract fingerprints is on a paper with a smooth surface and no water absorption. Dry 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, 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 wood, fur and other carriers.
Paper is the most representative of them.
Because paper is composed of plant fibers, which are invisible to the naked eye, but in fact there are large gaps between the fibers and the flatness is extremely poor.
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.
Thereby developing fingerprints.
But this method has a disadvantage, that is, it will destroy the fingerprint.
In other words, the chemical substances remaining in the fingerprint can only undergo one chemical reaction.
Afterwards the fingerprints will disappear and traces 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 non-destructively.
Then, neither iodine fumigation nor ice sampling methods will work.
“Old Liu, those hard-working people at the Technical Appraisal Center, if they can’t do it themselves, let the economic investigation come to us.”
Bai Wenhai was obviously a little emotional: "Why don't we reply and say no, forget it."
Liu Guodong looked at the envelope, folded his arms and 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, do you have any idea?"
Lu Chuan did not hesitate: "There is a way, but we don't have the relevant equipment, so we use ordinary It is basically impossible to extract fingerprints losslessly.”
Liu Guodong's eyes lit up after hearing this. "What can we do?"
Lao Bai also came over and listened to Lu Chuan's words: "Variable frequency laser spectrum analyzer."
Huh?
“What is this?”
Lao Bai has obviously never heard of this thing.
“The lasers that have been 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 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, 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, using this fixed-wavelength laser to collect biological samples cannot develop fingerprints on paper."
"The wavelength band needs to be adjusted."
Lu Chuan did not say specifically. What is the 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 fingerprints and leave traces, only the one I mentioned method.”
"How much does that instrument... 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, take a look at the car they configured.
A full set of BBA is available, even high-end ones.
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 required non-destructive fingerprint extraction this time is because the envelope has 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 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 has a wide range of uses. We sell it in Haizhou City."
In fact, Lu Chuan didn't know the exact price at first, but he was in Tianzhou the day before yesterday. Used by the Municipal Criminal Investigation Detachment.
I asked Li Kai about the equipment.
"More than four hundred thousand..."
It's not a big problem.
Liu Guodong packed up the letters and left the office directly: "Xiao Lu, wait for me in the office!"
Three hours later, when he 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... is this?"
Lu Chuan did not 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 with fingerprint analysis. This thing is borrowed by our detachment for free!"
Tsk tsk.
Lao Bai circled the instrument half a circle and said: "The economic investigation is rich, more than 400,000, and it can be approved so quickly!"
Liu Guodong agreed very much with Lao Bai's words: " They have 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 you. Good news!”
“No problem!”
(End of this chapter)