Diary of a Criminal Investigator-Chapter 253: Overlapping Fingerprints

The case handled by the Criminal Investigation Team of Taizhou City can be said to be quite a failure.

The real culprit was not found, and an innocent person who was wrongfully accused committed suicide in the detention center.

Lu Chuan can even imagine how terrified the detectives of the Taizhou City Criminal Investigation Team must have been when they saw the photos sent by the restaurant owner.

And the five blood-written words left by the deceased on the wall of the detention center.

"I am innocent!"

Even though Lu Chuan was not at the scene, he could imagine how much helplessness and indignation these words conveyed.

"What do they want us to do?"

Liu Guodong sighed deeply.

The Criminal Investigation Team of Taizhou City managed to handle the case to such an extent, yet now they are seeking assistance, certainty having discovered something they couldn’t solve on their own.

"Blood fingerprints."

Qin Yong pulled out the blood-colored fingerprint found on the murder weapon from the file.

"The most critical evidence that the Taizhou City Criminal Investigation Team used to identify the suspect is this blood fingerprint."

Lu Chuan nodded; in typical criminal cases, fingerprints are the most crucial piece of evidence.

Any fingerprint found at the crime scene is the most important evidence that the Crime Scene Investigation must focus on.

Moreover, this fingerprint was found on the murder weapon.

In fact, not all crime scenes can yield fingerprints.

Statistically speaking, only about twenty percent of criminal cases, if not fewer, can be solved through fingerprints.

For instance, the fingerprint battle organized by the provincial department involved not a particularly large number of criminal cases.

Additionally, fingerprint collection can be categorized into effective and ineffective.

Some scenes allow for fingerprint collection, yet not the criminal’s.

On other occasions, even if the criminal leaves behind fingerprints, they might not be collected.

Lu Chuan’s Fingerprint Collection Skills are specifically tailored for fingerprints.

"Because of this fingerprint, the investigating officers at the time immediately identified the so-called suspect who committed suicide in the detention center."

"They ignored some of the alibi evidence the other party presented."

This point is noted in the case file.

The innocent person was at a restaurant during the event, although there were no surveillance cameras, the owner hadn’t a strong impression of the deceased.

However, cameras surrounded the restaurant area.

Yesterday, the Taizhou City Criminal Investigation Team found a video from a surveillance camera two hundred meters away from the restaurant, showing the innocent person passing by during the time of the crime.

This further corroborated the photo evidence that the restaurant owner provided.

"After figuring things out, they conducted a more thorough fingerprint analysis and discovered this."

Qin Yong pulled out another printout sheet.

"There seems to be another layer of fingerprint over the fingerprint."

The print lines on the paper still showed the blood fingerprint, almost identical to the previous image.

But with Lu Chuan’s ability, he knew from the moment he saw this image that they had indeed made a mistake.

"Someone simulated the innocent’s fingerprint using a fingerprint mold."

Qin Yong wasn’t surprised that Lu Chuan noticed this.

"Indeed, the Taizhou City Criminal Investigation Team sent the fingerprint to the Provincial Technology Identification Center yesterday afternoon, but they also couldn’t extract it successfully."

"The suggestion from the provincial department is for you to take a look."

"Do you have any confidence?"

Lu Chuan frowned.

This type of overlapping fingerprint isn’t uncommon.

Most crime scenes feature overlapping fingerprints.

There are certain methods and techniques for separating such fingerprints.

Fingerprint identification experts from the provincial department, like Tian Rong, are also known to Lu Chuan from the last fingerprint battle.

Logically, overlapping fingerprints wouldn’t pose much difficulty for analysis by experts like Tian Rong.

The reason the provincial department couldn’t handle this fingerprint was due to one factor.

The overlapping fingerprint was too faint.

The perpetrator likely wore some kind of fingerprint mold glove during the crime.

The fingerprint left on the murder weapon belonged to the innocent suicide victim, while the real culprit’s fingerprint was imprinted on the mold through pressure.

Due to the uneven texture of fingerprints, it caused an imbalance in mold pressure.

Therefore, a web-like delicate fingerprint layer covered the blood fingerprint.

Lu Chuan’s current task is to separate the web-like fingerprint from the blood fingerprint.

Then, compare it within the system.

"I haven’t done this type of fingerprint identification analysis before, I’ll take it back and give it a try."

"Alright, if it works, it works, if not, we can’t help it. After all, even the experts at the provincial department couldn’t succeed."

Qin Yong wasn’t under much pressure, really.

Since the Taizhou City Criminal Investigation Team sought help, naturally there was no reason not to assist.

However, no one can guarantee success.

Crime Scene Investigation Office.

Lu Chuan was staring blankly at the computer.

Typical overlapping fingerprints can be handled well through image layering.

But only if the overlapping fingerprints are relatively clear or have similar depths in marks.

However, this particular fingerprint clearly doesn’t work.

The real culprit’s fingerprint was left very indistinctly due to the fingerprint mold glove.

The graphic software couldn’t even recognize the existence of overlapping fingerprints.

Lu Chuan had also tried using numerical transformations and data enhancement methods just now.

The data flow of the blood fingerprint is much more massive compared to the web-like covering fingerprint, making data separation difficult, let alone enhancement.

"How’s it going, not easy to handle?"

Old Bai handed Lu Chuan a cigarette.

Previously, when Lu Chuan did fingerprint identification, he would generally have the data flow on one screen; within ten minutes, half an hour, or at most, one or two hours, the results would be out.

Although Old Bai couldn’t understand the entire process, he could clearly sense a sense of confidence in handling the task.

This time was different; Lu Chuan had been staring blankly at the fingerprint on the computer screen for half an hour without making a move.

Taking the cigarette, Lu Chuan nodded.

"The overlapping fingerprints are too faint, and general methods can’t extract them; I need to study it."

"Take your time; if you can’t solve it, probably no one in our province can."

After participating in the fingerprint battle organized by the provincial department last time, Lu Chuan had already been subtly recognized as the top fingerprint identification analyst in the province.

Recently, several other city criminal investigation teams have approached for assistance.

With math transformations being unhelpful, and the built-in image layering of the software unable to identify, Lu Chuan studied for a while and decided he could only rely on his programming skills.

In fact, the most essential part of separating and extracting overlapping fingerprints is layering the image.

Yet the method Lu Chuan adopted was rather complex.

The underlying blood fingerprint is darker in color and more pronounced in lines, while the covering fingerprint on top is lighter in color and finer in lines.

Given this, the grayscale value of each fingerprint ridge differs greatly.

The grayscale values of the blood fingerprint and the covering fingerprint fall into two distinct ranges.

Theoretically, if Lu Chuan can distinguish the image’s grayscale value and then extract images from different grayscale value areas, he can separate the two overlapping fingerprints.