Chapter 26: Fingerprint Developer

“Xiao Lu, the handlebars are the key. Whether the suspect was pushing the electric scooter or riding it, the handlebars are a part they must have touched.”

Yang Sen mimicked the posture of someone riding an electric scooter, analyzing the areas the killer might have touched.

“There is no human habitation within two kilometers of the Xingfu Reservoir, so it is unlikely the suspect was pushing the scooter...”

Liu Guodong picked up a high-intensity flashlight and shone it on the scooter's floorboard, carefully observing whether any footprints remained.

If they were pushing the scooter, they wouldn't touch the floorboard; but if they were riding it, they would inevitably leave footprints there.

Lao Bai was busy cleaning hair out of the rear wheel bearing: “The body was likely draped across the rear seat at the time; that’s how the hair got tangled in the bearing.”

*Ding!*

“Advanced Task: Through the examination of the electric scooter, collect fingerprint information to help the action group narrow down the suspect pool and solve the Xingfu Reservoir Body Dumping Case.”

Lu Chuan, having accepted the task, turned his attention to the rear grab rail.

To push the scooter into the reservoir, the killer's fingers would very likely touch the rear grab rail.

While Lu Chuan and the others were examining the scooter, the detectives from the action group were also rapidly advancing their work.

“Captain Qin, we’ve identified the origin of the electric scooter.”

Ren Qiang held up the registration information provided by the traffic police: “The owner is named Wang Song; he runs a small restaurant.”

“It was stolen three days ago. The local police station has a report on file from Wang Song.”

Three days ago was exactly when the victim was murdered.

“Where was the scooter stolen from?”

“No. 28 Beihu Road, right in front of Wang Song’s restaurant.”

“Is there surveillance footage?”

Ren Qiang shook his head: “The vehicle was parked in a blind spot of the cameras. No trace of the thief was found.”

“Investigate. Conduct a focused screening of this Wang Song,” Qin Yong thought for a moment before assigning the next tasks.

Qin Yong had seen plenty of cases of employees stealing from their own employers.

“Also, contact the traffic police. The killer stole the scooter to dump the body, so there will definitely be video footage along the route.”

“Identify every road segment between No. 28 Beihu Road and Xingfu Reservoir. Pull all surveillance footage—don't let a single frame slip through!”

This was the essence of a homicide investigation mechanism: to exert the maximum possible effort, deploy the most resources, and solve the case in the shortest possible time!

Inside the brigade courtyard.

Liu Guodong and the others looked at the electric scooter before them with grim expressions, feeling somewhat helpless.

“Old Liu, the scooter has been submerged in water for too long. It’s impossible to extract fingerprints.”

An entire afternoon had passed without any progress from the forensic team.

On the other hand, Lao Bai had already completed the DNA comparison.

The hair in the rear wheel bearing belonged to the deceased.

At this moment, only Lu Chuan was crouching on the ground, scanning every inch of the scooter's components.

Liu Guodong recalled the fingerprints Lu Chuan had extracted from the corpse this morning, which were exceptionally complete.

He also remembered how Lu Chuan had helped Ren Qiang’s second action group extract fingerprints at the South Suburb arson scene a few days ago.

Combined with Lu Chuan’s current meticulous and serious demeanor, a glimmer of hope rose in his heart.

“Xiao Lu, do you have any ideas?”

Although Lu Chuan’s brow was slightly furrowed, his expression remained relatively relaxed.

The intermediate fingerprint collection skill rewarded by the system included many techniques and methods.

In particular, there were specialized collection methods for fingerprints affected by fire or water immersion.

Even though this scooter had been submerged for three days, Lu Chuan still had a way to collect the residual fingerprint information.

“Master, I’ve made some discoveries.”

Lu Chuan took a UV lamp from the forensic kit and shone it on the handlebars, the rear seat, and the floorboard.

“I have observed these areas closely; there are no signs of wiping.”

Liu Guodong nodded: “There are indeed no signs of wiping. There should be fingerprints on them, but after being submerged in water, they simply cannot be extracted.”

Liu Guodong had already tried; neither standard physical nor chemical methods could extract the prints.

After three days of immersion, the sweat that formed the fingerprints had long since dissolved.

Even the water-insoluble components of the oils had faded so much through prolonged immersion that they could no longer be developed.

In forensics, water-related cases were the most dreaded.

The longer the time elapsed, the less there was to find.

Lu Chuan nodded: “Conventional methods indeed cannot extract fingerprints after immersion, but certain specialized methods might still be effective.”

Turning off the UV lamp, Lu Chuan’s brow relaxed: “It’s just that there will be some issues regarding the completeness of the fingerprints.”

Oh?

There were issues with completeness, but it wasn't impossible?

Liu Guodong’s eyes brightened: “Xiao Lu, are you saying they can still be extracted?”

“Yes, but I need to prepare something.”

An hour later.

Lu Chuan returned to the courtyard.

This time, he was carrying a small spray bottle.

During this hour, Liu Guodong and the other two had followed Lu Chuan around.

They had personally witnessed Lu Chuan evolve from a criminal investigator into... a chef.

Yes, a chef.

The guy had spent the last hour wandering around the brigade's kitchen.

He had rummaged through every bottle and jar inside.

And had concocted this dark, murky liquid.

“Xiao Lu... can this... actually work?”

Lao Bai was somewhat bewildered. Although he didn't understand the technical details of what Lu Chuan was doing, he knew Lu Chuan was making his own fingerprint developer.

But wasn't this something only legendary experts were supposed to do?

Lu Chuan... was making his own fingerprint developer?

Liu Guodong’s gaze sharpened as he looked at the small spray bottle in Lu Chuan's hand: “Lu Chuan... are you sure you can do this?”

The criminal investigation brigade had fingerprint developers; they were issued by the higher authorities.

The ingredients were actually quite simple, primarily water and some chemical coagulants.

This type of developer was standardized nationwide, had a stable structure, and was a commonly used material for forensic fingerprint extraction.

However, before the standardized issuance, every region had its own commonly used developer.

Historically, there had been many instances where unstable developers destroyed the fingerprints at a crime scene.

Therefore, the use of self-made fingerprint developers had been prohibited.

On one hand, Lu Chuan's ability to make his own developer indicated that his fingerprint collection skills had already surpassed those of Liu Guodong and the others.

On the other hand, if the developer caused problems and destroyed the fingerprints on the scooter, the responsibility would fall entirely on Lu Chuan.

If the fingerprints couldn't be collected because the scooter had been submerged for three days, it was normal, and no one could blame the forensics office. At worst, they would report it to the provincial department and have experts come to investigate.

But if the developer destroyed the fingerprints, even the experts from above wouldn't be able to collect them.

Then, the responsibility would belong to Lu Chuan.

This was also why cutting-edge technology was rarely applied in the field of criminal investigation.

Seeking stability was the lifeline of criminal investigation.

Lu Chuan clearly understood the implication in Liu Guodong's words.

He was concerned for him.

As for hiding the use of the developer, that was impossible.

Fingerprint developer is a chemical substance; its use will inevitably leave traces.

These must be recorded; it is a matter of procedure that no one can violate.

So, should Lu Chuan take the risk?