Chapter 79: Chapter Seventy-Nine: A Peaceful Atmosphere

Afternoon.

Sunlight spilled across the courtyard, filling it with a peaceful aura.

Only six criminal investigators labored tirelessly to send seven people—and more—into prison.

“Magnetic powder will work.”

“Use ultraviolet light first.”

“This one… ninhydrin.”

Jiang Yuan spent several hours at the crime scene and easily gained authority over its procedures.

A few officers initially struggled to adapt, but gradually grew accustomed to Jiang Yuan’s methods.

At this crime scene, it was like a workshop or an office—where the presence of a skilled technician ultimately steered everyone toward a unified or similar technical standard; otherwise, work could not proceed.

As for fingerprints alone, the prints collected by Ningtai County’s field investigators were handed to Yan Ge and Wang Zhong for analysis. Their requirements were simple: clarity and accuracy. If they couldn’t produce results, they said nothing, merely accepting it as their own inadequacy.

Jiang Yuan’s standards were vastly different, because he knew exactly what he was capable of achieving. For fingerprints destined for comparison or database entry, his requirements were naturally far higher.

But the most crucial point was that Jiang Yuan could provide clear, actionable solutions to obtain crisp fingerprints.

Several field investigators hadn’t received such “instruction” since leaving school.

Take ninhydrin, for instance—it should be the most commonly used technique, taught in textbooks and classrooms, and routinely applied at countless crime scenes.

It’s a chemical reaction with a complex mechanism, but in effect, the ninhydrin method clearly reveals latent fingerprints on light-colored paper, documents, and even wooden surfaces. It’s an excellent, powerful solution.

Yet in real crime scenes, criminal investigators rarely used this method.

Without exaggeration, the most common, most frequently used, and often the only method employed in most field investigations was powder development.

“One brush solves everything” was the daily reality for most criminal investigators.

And they didn’t even bother switching powder types.

The technicians on today’s field investigation were all from the Criminal Science Unit. Occasionally, they still used ninhydrin and 502 fuming—but today’s full-scale deployment was why so many technicians were out in the field.

Normally, for minor cases, responding officers and police station personnel would simply lift fingerprints on-site and enter them into the database, yet many of them had no idea how to use ninhydrin or 502 fuming.

In fact, due to infrequent use, even the Criminal Science Unit’s technicians weren’t very proficient with ninhydrin or 502 fuming.

This was easy to understand: if a person walks the same route to work every day and always arrives without issue, why change routes unless some unexpected event blocks the path entirely?

The technicians of Ningtai County operated exactly this way: if a fingerprint could be lifted with powder, they used powder—no exceptions.

They didn’t even bother switching powder types.

Only when dealing with non-smooth surfaces, textiles, or fingerprints that powder simply couldn’t reveal—and only if those prints were critical—would a technician resort to ninhydrin.

It was like avoiding detours during wind and rain: as long as the road wasn’t washed out or completely blocked, they never changed course.

Previously, the task of analyzing fingerprints fell to Yan Ge and Wang Zhong; now, it was Jiang Yuan.

Jiang Yuan was like a company demanding punctual attendance and relentlessly reducing commute time. For field technicians to meet his standard, choosing the right method became vital.

More importantly, everyone was willing to reduce their “commute time”—or rather, willing to cooperate with Jiang Yuan to improve the quality of database entries.

In criminal science, this was a martial arts manual: the foundation for survival and self-improvement, a tool to elevate both work and self. Doing work was doing work—most people still preferred to do it well.

But anything worth doing well always carried some difficulty.

Take ninhydrin: anyone who’d spent three or four years in police academy could confidently declare, “I know this well.”

But ask them: “What’s your standard ninhydrin formula?”—eight out of ten would fall silent.

Only technicians like Wang Zhong, who had actually used ninhydrin, could effortlessly recite: “One gram of ninhydrin and one hundred grams of anhydrous ethanol. We used acetone more often before, but now regulations are stricter—we can’t get much acetone anymore…”

Jiang Yuan responded without mercy: “Add ether.”

“Huh? A formula with ether? Add… sixty grams?” Wang Zhong, trying to recall the formula on the spot, clearly didn’t remember clearly.

Jiang Yuan said: “Use two grams of ninhydrin, then 33.5 grams of anhydrous ethanol, then 66.5 grams of ether. The latent print you’re developing is on a polymeric surface—adding ether will make it dramatically clearer. Your earlier one-to-one-hundred ethanol formula works fine on paper, but it won’t work well on polymeric surfaces.”

“My mind’s gone blank—I learned this formula before,” Wang Zhong slapped his forehead. He’d studied it, but after years of never using it, the details had vanished.

Wang Zhong immediately mixed the ninhydrin solution and brushed it onto a kraft paper bag.

Jiang Yuan opened his mouth slightly but made no further demands.

Ninhydrin development took one to two hours, but there were ways to speed it up. Still, time was ample, so Jiang Yuan saw no need to nitpick.

With no further questions, Jiang Yuan selected non-smooth surfaces and began working himself.

Criminal investigators traditionally assumed fingerprints were found only on smooth surfaces. Or rather, given their skill level, simply clarifying fingerprints on smooth surfaces was already difficult enough.

Jiang Yuan pulled a glue gun from his field kit.

He sprinkled powder onto the surface of a vintage LV monogram handbag, raised the glue gun, and sprayed a thick, viscous liquid with a hiss, then heated it with a hairdryer.

Several nearby field investigators stared, dumbfounded.

“We have this equipment?” the field investigators wondered, baffled.

“Found it in storage,” Jiang Yuan said, holding the glue gun and moving around confidently. “Probably bought as a complete set.”

“Of course—everything’s bundled now…” The field investigators looked helplessly resigned, suddenly realizing they knew nothing about their own department’s inventory.