Chapter 182: The Old Trade

Using fingerprints to solve cold cases has always been Jiang Yuan's specialty.

The plaque honoring him as a Second-Class Merit recipient still sits outside his front door, polished daily by his father until it gleams.

Having processed so many cold-case fingerprints, Jiang Yuan immediately saw matching potential in the blood print on the leather jacket.

This was confidence rooted in personal ability.

First, the clarity of blood fingerprints is usually acceptable. Though this print was lifted from a leather jacket and slightly degraded, it was still far superior to most latent sweat prints.

Second, though the fingerprint covered only one-third of the area and lacked a core, it included the fingertip—a highly individualized feature.

In standard forensic work, if a fingerprint lacked a core or had a blurred one, investigators would abandon it outright, as such prints were nearly impossible to match.

But for Jiang Yuan, as long as he could accurately determine the core's position and the surrounding ridge lines were clear, he could extract a match. His success rate was only slightly lower than with prints lacking a core entirely.

For active cases, naturally, the better the fingerprint quality, the easier the match.

But after handling so many cold cases, one basic truth had long been clear: for cold cases, the clearer the fingerprint, the less meaningful it was.

A fingerprint anyone could match was like a dog that licked everyone—it had no owner.

Of course, the difficulty of this fingerprint was obvious.

Jiang Yuan downloaded the fingerprint image onto his computer and stared at it without moving.

At that moment, a system message flashed before his eyes:

……

Task: Crack the Cold Case

Task Content: Solve Case 405—Xu Hai

……

Jiang Yuan cross-checked: Case 405—Xu Hai was precisely the case he had just selected.

This saved him the trouble of worrying whether to switch cases if he hit a wall.

He would focus entirely on smashing this one.

Jiang Yuan rubbed his hands. Old habit: regardless of fingerprint quality, start with image enhancement.

As the saying goes: Photoshop three times, and even beauties can't stand steady.

A fingerprint after enhancement was like a leader who'd drunk Maotai—it was bound to reveal something real.

Jiang Yuan didn't need much: on a full fingerprint, you'd mark fifteen features; on this one-third print, if he could extract eight, he'd have a basis for comparison.

The old high-performance host hummed to life.

Wu Jun lifted his head: "You picked a case?"

"Case 405—Xu Hai," Jiang Yuan said.

"Tell me about the body, and I'll know," Wu Jun said, standing and lighting a cigarette.

Jiang Yuan cut straight to the point: "The body was found beside a rural road in Litang Township, about eight meters from the road, blocked by trees and vines. The corpse was highly decomposed, with stab wounds to the abdomen and chest…"

"Ah, I get it—the victim was a street vendor who sold clothes?" Wu Jun's tone carried the weight of history.

Jiang Yuan grunted. "I noticed a blood print on his leather jacket. I want to compare it."

"Fingerprints, huh? That's doable," Wu Jun said, then couldn't resist adding: "This case is tough."

"Where did it stall back then?" Jiang Yuan asked, curious.

Wu Jun didn't answer. Instead, he asked: "What's your take on the nature of this case?"

Jiang Yuan was focused on the fingerprint but had skimmed the case file. He thought a moment. "Roadside robbery that escalated to murder?"

"Then why eight meters from the road? The crime scene photos include a close-up of the roadside vegetation—look at how dense it is. Getting there wasn't easy. If you were forcing someone at knifepoint, it'd be risky."

Jiang Yuan pulled up the internal network photos—the cold case images, digitized clearly. The plants just two or three meters from the road were thick; reaching eight meters meant pushing through, not walking. If the killer had forced the victim there at knifepoint, it'd be prone to mishaps.

Of course, that mishap might've been the trigger for escalation?

Jiang Yuan didn't fully grasp it, but understood Wu Jun's point. "So back then, you thought it wasn't a robbery?"

Wu Jun shook his head. "I thought it was. Many thought it was. But the leadership didn't."

"Why?"

"Because if it was a robbery-turned-murder, this case couldn't be solved," Wu Jun said, spreading his hands and sighing. "And there's logic to it. Back then, investigations relied on three moves: inspect, screen, interrogate. Out here in the wilderness, labeling it a robbery-murder made the case nearly impossible."

"Inspect, screen, interrogate" meant crime scene examination, door-to-door canvassing, and surprise interrogation.

This method relied on a stable social network.

After the founding of the PRC, the household registration system drastically reduced population mobility. Most crimes were committed by acquaintances; screening could yield satisfactory clearance rates.

Those outside the system—migrant workers—were labeled "blind flow" by police, routinely detained, interrogated, and repatriated.

As social mobility increased, police effectiveness plummeted, and public security deteriorated further.

Wu Jun hadn't told Jiang Yuan this: back then, roadside robberies were fairly common, so leadership had little motivation to solve them.

Jiang Yuan asked curiously: "What did Chief Huang say back then?"

"He was chief of the police station then," Wu Jun paused, recalling. "This case probably got him promoted to head of the Criminal Investigation Unit."

Jiang Yuan couldn't help pressing: "Was the previous head replaced because of this case?"

"Something like that. There were plenty of unsolved cases those years."

Seeing Wu Jun wasn't inclined to elaborate, Jiang Yuan returned to the case. "So you think the main issue is direction?"

"The victim's social network was thoroughly screened—no results," Wu Jun said, shaking his head. "Focus on the fingerprint. That's the only thing left that might yield something."

Random crimes were hard to solve back then; now, impossible.

Over the years, most solved cold cases relied on fingerprints and DNA—same reason.

Many leads were untraceable then, and now, utterly lost.

Jiang Yuan had hoped his mentor could offer more insight. Much of what matters isn't written in case files.

What Wu Jun just described—discarded investigative directions—fell into that category.

But for now, it was useless.

Jiang Yuan stopped overthinking and turned back to the fingerprint.

Just like during the provincial fingerprint blitz in Changyang.

Back then, no one helped you—you simply worked fingerprints. Match it, and you succeeded; fail, and you went home empty-handed.

Half the provincial fingerprint experts, all LV3-level trace analysts, returned home with zero matches.

Jiang Yuan processed one fingerprint—and it was already quitting time.

Wu Jun stood on schedule. "Leaving?"

"I'm staying late," Jiang Yuan sighed, pulling out his phone to text his father.

Wu Jun smiled. "Balance work and rest. Take a break."

"You break the flow," Jiang Yuan said, shaking his head helplessly.

Why did fingerprint experts perform better during the provincial blitz? Partly due to attention, but mostly because they could focus entirely on fingerprints—even skip going home.

Jiang Yuan wouldn't take this blood print lightly. Returning to his blitz-state mindset was his best advantage.