Putting down the tea watch, Lu Chuan continued to conduct technical identification and analysis of the garbage inside the garbage bags.
Lu Chuan has extracted corresponding amounts of some of the toilet paper and vegetable residues and sent them to the technical appraisal center in the provincial capital for trace evidence analysis.
The Dongzhou City Criminal Investigation Detachment does not have the ability to analyze trace species, so these technical identification tasks require support from the Technical Identification Center in Shengcheng.
The results will not be available until noon tomorrow at the earliest.
From Lu Chuan's perspective, this case may not be particularly difficult to detect.
Because the bodily fluids left by the criminal suspect in the body of the deceased have been extracted from the victim's DNA information.
The current case is determined to be the work of the Red Killer because the DNA information extracted from the victim's body is consistent with the DNA information extracted from the other 10 people.
So as long as the same DNA material is found in the plastic bag, it can be determined whether the plastic bag was thrown by the murderer.
At the same time, if other clues can be used to determine who the person who locked the plastic bag belongs to, then the case may be solved.
Of course, this is only a theoretical statement. In fact, it is still uncertain whether the suspect can be identified.
Because in the process of solving previous cases, the Dongzhou City Criminal Investigation Detachment also found major clues.
With the addition of crime-solving experts from the provincial department and experts appointed by ministries and commissions to investigate the cases, Lu Chuan found many pointing clues in some files.
Unfortunately, 15 years have passed and although there are many clues, the case has not been solved and the suspect has never been caught.
Another difference in this case is that the fingerprints and footprints left at the crime scene are not the same.
DNA information proves that the suspects in these cases are all the same murderer, but the fingerprints and footprints extracted at the crime scenes do not point to the same person.
This is interesting.
Did this person have other murderers assisting him when he committed the crime, or did the other murderer imitate other people's fingerprints or footprints?
Soon Lu Chuan made some progress.
The method of extracting fingerprints from plastic bags is different from that of other ordinary fingerprints.
The general powder method is not possible. The method Lu Chuan adopted is a combination of the powder method and fluorescent lamp irradiation.
It is easy to find fingerprints, but it is more difficult to extract them and then perform technical identification and analysis on them.
Lu Chuan generally uses a combination of multiple methods to extract fingerprints.
In this way, the occurrence of fingerprint breakpoints can be greatly reduced, and the probability of success may be greater during the fingerprint identification and analysis process.
The fingerprints collected on plastic bags are mainly on the edges of the handles.
However, due to the irregular shape of the edges, the fingerprints are very seriously broken.
Previously, the detectives from the Dongzhou City Criminal Investigation Detachment also planned to extract fingerprints from the plastic bags, but they were unsuccessful.
The main reason is that these fingerprints are too fragmented and not formed at all. Even if they are extracted, they are a scattered pile that cannot be spliced together, let alone analyzed.
The fingerprint extraction this time was also a great challenge for Lu Chuan. He had never extracted fingerprints from this kind of plastic bag when solving crimes before. The most important step after fingerprint extraction is the splicing of fingerprints.
Even with Lu Chuan’s top fingerprint identification technology analysis skills, it was quite laborious to do.
Lu Chuan wanted to sort out these broken fingerprints one by one, and then virtualize the lines and breakpoints of these fingerprints.
This cannot be accomplished through computer or other auxiliary means. Lu Chuan can only compare it slowly by himself.
Not only are everyone’s fingerprints different, but this difference is reflected in multiple dimensions.
The first type is the specific shape of the fingerprint, which should be divided into three types: bucket type, bow type and skip type.
It is very simple to classify fingerprints in this specific situation, and even ordinary people can distinguish them.
For Lu Chuan, this kind of classification and analysis of specific shapes is completely unable to satisfy his fingerprint identification.
Most of the fingerprints left at the crime scene in general cases are obvious fingerprints, that is, fingerprints left on hard objects, such as desktops and floors.
This kind of fingerprints are generally visible to the naked eye. In many crime scenes, blood fingerprints, for example, fall into this category.
Another type of fingerprint that detectives often encounter during investigation is shaped fingerprints.
This kind of fingerprint is usually a fingerprint left on a soft carrier, such as a candle on clay. The fingerprints remaining on the substance are all formed fingerprints.
Most of the fingerprints analyzed during the investigation of crimes are actually the third type of fingerprints, called latent fingerprints.
Fingerprints are invisible to the naked eye and must be identified in some way with the help of instruments such as ultraviolet lamps.
The main way latent fingerprints remain is through adsorption of oil and sweat.
Theoretically, latent fingerprints can occur on the surface of any object.
Lu Chuan analyzed and sorted out these broken fingerprints. The most important thing was to conduct a virtual analysis of the grain directions of these fingerprints through the identification of feature points.
Different people's fingerprints have different bifurcation points, ending points, and intersection points.
However, the fingerprint points of the same person will also have different trend distributions. What Lu Chuan has to do now is to sort out these broken fingerprints one by one, and then find the fingerprints that are similar in width, similar and identical in texture. . These fingerprints of trends are then spliced together to try to restore a complete fingerprint.
This is a technical job and a time-consuming job. Generally speaking, a fingerprint like this is analyzed by Lu Chuan. It will take several hours to get down, or even a day, of course, it may take longer.
The fingerprints extracted from the garbage bags were too fragmented, and due to their irregular positions, it might take Lu Chuan a day or even longer to piece them together this time.
But for a top-notch fingerprint like Lu Chuan, first look at the criminal police. As long as the fingerprint exists, the other party will definitely not be able to escape.
Even if there is no fingerprint of the target person for comparison in the system, as long as Lu Chuan targets this fingerprint, it is possible to successfully compare it by collecting it from all suspected criminal suspects.
While Lu Chuan was carefully investigating and analyzing the black plastic bags, other groups were also advancing their work.
And there has been some progress. (End of this chapter)