National Forensic Doctor

Chapter 1354: Chapter 1280: Screening

"The coffee is pretty good." Liu Jinghui took another cup of coffee and drank it in one gulp, then returned to verify the timeline.

Wei Shikan observed his oblivious demeanor and then looked at Jiang Yuan, who was deep in thought in front of the computer, before shaking his arms to brew another cup of coffee.

"Shikan." Jiang Yuan suddenly raised his head and called out.

"Ah! Master." Wei Shikan immediately stepped forward.

Jiang Yuan scrutinized Wei Shikan for a moment and said, "I’ve seen the practice problems you’ve been working on recently; there’s noticeable improvement."

"Ah... That’s because you taught me well." Wei Shikan felt thankful for the countless nights he and his senior sister endured.

"Did you understand the steps for image enhancement I just demonstrated?" Jiang Yuan asked again.

"Still a bit off," Wei Shikan replied with a couple of awkward laughs, "The steps are quite complex; I might need to study for a bit longer."

"You can give it a try," Jiang Yuan said, gesturing for Wei Shikan to sit beside him.

A knowledgeable local technician immediately moved a set of computer and monitor next to Wei Shikan.

Before Wei Shikan could object, the computer screen in front of him lit up.

As he looked at Jiang Yuan on his left and then at the screen in front of him, he felt somewhat like he was taking a test next to a teacher.

"If you hit a wall, just say so. You can try multiple approaches; there’s no need to get stuck on one path," Jiang Yuan said as he checked the software on the computer and threw a few bundles of video files to him.

Wei Shikan hesitated and said, "My math hasn’t really improved..."

"As long as you know how to use the software, that’s enough. Whether you can upgrade depends on your talents later," Jiang Yuan waved his hand, signaling Wei Shikan to get started.

Wei Shikan nodded with difficulty, like an agreeable golden snub-nosed monkey, carefully opening an original video, first making a backup and performing a hash value check.

After confirming the video format, Wei Shikan started preprocessing the video using Neat-Video for noise reduction, trying to minimize grain noise or compression artifacts. He then performed multi-frame averaging for temporal noise reduction, using Gaussian blur and median filtering for spatial noise reduction. Though it was the software doing the work, merely entering all sorts of values was enough to overload Wei Shikan’s brain.

He glanced at Jiang Yuan, who seemed to resolve any issues as he scanned through surveillance videos by quickly adjusting software settings with a few keystrokes, many values changing rapidly.

To the untrained eye, Jiang Yuan might appear to be in a state of practiced ease, but only Wei Shikan knew this was the state of skilled calculations.

Just as ordinary people know sin45 degrees equals the square root of two over two, approximately 0.028, the standard deviation for Gaussian noise in low-light surveillance is commonly between 1.5 and 2. But when retaining edges, you might choose 1.0, or switch to bilateral filtering; however, oftentimes, you’d rely on the GaussianBlur function, calculated based on kernel size...

Compared to before, Wei Shikan had already grasped many principles, but Gaussian noise was only a minor step in the preprocessing stage...

A few hours slipped by in a flash.

During the break, Jiang Yuan remembered Wei Shikan, walking over like a school teacher. He saw two computer screens in front of Wei Shikan; the screens were lit, the cursors blinking, and Wei Shikan’s eyes open, but that was it.

"Hit a bottleneck?" Jiang Yuan inquired gently.

Having taken on the second generation’s task, he’d need to see it through. noveldrama

Wei Shikan glanced up at Jiang Yuan in a daze and then shuddered violently, saying, "There are many bottlenecks."

"Where did you get stuck..." Jiang Yuan remained calm. Being exceptional himself, he was aware of the difficulties in Image Investigation. This stuff is such that any normal person would become atypical upon touching it. Fortunately, Wei Shikan wasn’t entirely normal to begin with.

Wei Shikan looked up sheepishly, "I wanted to remove motion blur using Wiener filtering, but it turned into a mess..."

"Then use blind deconvolution with focus-magic; I’ll teach you how to adjust it," Jiang Yuan stood behind Wei Shikan, guiding him bit by bit.

Several Dama technicians stood in front, eyes wide open, listening intently. Zhong Renlong did his best to translate, but faced with the long string of technical terms and numbers, his voice grew increasingly small.

"I’ve finished my side," Liu Jinghui said, his eyes red from too much coffee, walking over.

"Can you identify any suspects?" Jiang Yuan shifted his focus from Wei Shikan.

"Currently, there are four individuals without alibi evidence. Or rather, their alibi evidence is incomplete, though I’ve set quite strict criteria," Liu Jinghui paused and looked at Jiang Yuan, "I’ve based this on the death times of the three victims, narrowing it down to within four hours."

"Four hours is fine," Jiang Yuan nodded.

Jiang Yuan had made a temporary calculation, using a temporary Level 7 death time to determine the timeline. In theory, this time frame could be reduced, but when judging suspects based on this, Jiang Yuan preferred to err on the side of caution.

Liu Jinghui nodded, "Although there are three murder cases, the perpetrator’s timeline is during breaks, two during the day and one at night. The nighttime case left very little room for filtering, while the two daytime cases helped eliminate most suspects."

Liu Jinghui proceeded to display his and Wang Chuanxing’s results via a presentation on the projector screen.

After a dazzling introductory animation, each name was followed by their respective timeline.

In the three cases, especially the first two, the timeline of each person’s day, particularly the four-hour period surrounding the victim’s time of death, was meticulously organized.

Liu Jinghui used a laser pointer to indicate, "Looking at the timeline, the murderer did improve with each kill. For example, in the third case, the murder’s time and location made surveillance futile."

Liu Jinghui continued, "The four people I ultimately filtered out actually exceeded my initial expectation. I thought with a broad filtering of 23 people, even if we relaxed the criteria, it would only be one or two who fit all three murder timelines. I was even prepared for none. Then, we might have to consider the possibility of an outside perpetrator."

Liu Jinghui added, "But as it turns out, nearly half are primarily technicians working independently and not under surveillance most of the time. For example, those installing sunshade nets, doing machinery repairs, pruning, and planting, are mostly working outdoors and don’t even return for lunch, which provides opportunities for the culprit."

Liu Jinghui concluded, "All in all, the final four are production manager Li Wanzhong, mechanics Zhang Fan and He Jun, and general worker He Cheng."

Following his words, Wang Chuanxing expanded the profiles of the four individuals.

Liu Jinghui cleared his throat and said, "Among them, Li Wanzhong is the longest-serving employee in the rubber plantation and is currently the oldest. As one of the managers of the plantation, Li Wanzhong’s workload isn’t light, requiring him to spend most time in the office area. During the two murders, he had no alibi, which itself is a point of suspicion..."

"Hold on!" Ni Cha checked his phone and suddenly interrupted Liu Jinghui.

Everyone looked over.

Ni Cha showed the phone screen, "Li Wanzhong committed suicide in his room."