Chapter 1055: Lu Chuan’s Fingerprint Identification and Analysis

After putting down the tea, Lu Chuan continued the technical identification and analysis of the garbage in the trash bag.

Among the items were some toilet paper and vegetable residues. Lu Chuan had already extracted the necessary amounts and sent them to the provincial technical identification center for trace evidence analysis.

The Criminal Investigation Team in Dongzhou City does not have the capability for trace species analysis, so these technical identification tasks need support from the technical identification center in the provincial city.

The fastest feedback on the results will be by noon tomorrow.

From Lu Chuan’s perspective, the difficulty of solving this case may not be particularly high.

Because the bodily fluids left by the suspect inside the victim have already been extracted into the victim’s DNA information.

Currently, this case is confirmed as the doing of the Red-clothed Killer because the DNA information extracted from the victim’s body matches that extracted from the bodies of 10 other people.

Therefore, if the same DNA substance is found inside the plastic bag, it can be determined whether the plastic bag was discarded by the killer.

Meanwhile, if other clues can be used to identify the owner of the plastic bag, the case might be solved.

Of course, this is only theoretical; it is uncertain whether the suspect can actually be identified.

During previous investigations, the Criminal Investigation Team in Dongzhou City had also discovered significant clues.

With the involvement of provincial and ministry experts assigned to investigate the case, Lu Chuan found many directional clues in the files.

Unfortunately, 15 years have passed. Although there are plenty of clues, the case remains unsolved, and the suspect has yet to be caught.

This case has another peculiarity: the fingerprints and footprints left at the crime scene are not the same.

DNA evidence proves that the suspects of these cases are the same killer, but the fingerprints and footprints extracted from the crime scenes do not point to the same person.

This is intriguing.

Does this mean the perpetrator had the help of other killers during the crime, or did they simulate someone else’s fingerprints or footprints?

Soon Lu Chuan made some progress.

The method for extracting fingerprints from the plastic bag differs from the extraction of regular fingerprints.

The standard powder method doesn’t work; Lu Chuan used a combination of the powder method and fluorescent lighting.

It is easier to find fingerprints, but extracting and technically identifying them is quite challenging.

Lu Chuan typically uses a combined method for extracting fingerprints.

This significantly reduces the occurrence of fingerprint breakage, increasing the success rate in the fingerprint identification and analysis process.

The fingerprints extracted from the plastic bag were mainly along the edge of the handle.

However, due to the irregular shape of the edge, the fingerprints extracted were severely fragmented.

Previously, the Crime Scene Investigation police from Dongzhou City had also attempted to extract fingerprints from the plastic bag, but failed.

The main reason was that the fingerprints were too fragmented and shapeless; even if extracted, they were disjointed bits and couldn’t be pieced together or subjected to analysis.

This fingerprint extraction posed a significant challenge for Lu Chuan. He had never extracted fingerprints from such a plastic bag in previous cases.

After extracting the fingerprints, the most crucial step is piecing them together.

Even with Lu Chuan’s top-tier fingerprint identification and analysis skills, the task is quite labor-intensive.

Lu Chuan needs to systematically sort out the broken fingerprints and virtually process the ridge patterns and breakpoints.

This cannot be accomplished with computer assistance; Lu Chuan can only compare them himself, slowly.

Everyone’s fingerprints are different, and these differences exist across multiple dimensions.

The first dimension is the specific shape of the fingerprint, divided into three types: loop, arch, and whorl.

Using this criterion to classify fingerprints is relatively simple; even an ordinary person can distinguish them.

For Lu Chuan, classification and analysis based on specific shapes alone cannot satisfy his fingerprint identification needs.

In general cases, most fingerprints left at crime scenes are visible fingerprints, on hard objects like tabletops and floors.

These fingerprints are usually visible to the naked eye; in many crime scenes, bloody handprints fall into this category.

Another type frequently encountered by Crime Scene Investigation detectives is formed fingerprints.

These fingerprints occur on soft substrates, such as clay or candles, where fingerprints remain formed.

In the process of solving cases, most fingerprints analyzed are actually the third type: latent fingerprints.

The fingerprints are invisible to the naked eye and can only be identified using special techniques and tools, such as ultraviolet light.

Latent fingerprints are predominantly left by the absorption of oils and sweat.

Theoretically, latent fingerprints can occur on any object surface.

Lu Chuan analyzes and organizes these broken fingerprints mainly by identifying characteristic points to conduct virtual analyses of the ridge orientation.

Different people’s fingerprints have distinct divergences, termination points, and crossover points.

But with one person’s fingerprints, these points also display different distribution trends. Lu Chuan’s task is to sort out these broken fingerprints one by one, find the similar width and texture with these fingerprints, then piece them together to attempt recreating a complete fingerprint.

This is a technical task and a time-consuming job; generally, analyzing a fingerprint like this can take Lu Chuan several hours or even an entire day, possibly more.

The fingerprints extracted from the trash bag are overly fragmented and irregularly positioned, so this time Lu Chuan might spend a day, even longer, piecing them together.

But for a top-tier fingerprint investigator like Lu Chuan, as long as fingerprints exist, suspects can’t escape.

Even if a suspect’s fingerprint is not in the system for comparison, as long as Lu Chuan identifies the fingerprint, gathering samples from all suspicious suspects might yield a match.

While Lu Chuan meticulously examines and analyzes the black plastic bag, other teams are also advancing their work.

And there have already been some developments.