Chapter 129: Bloodstain Analysis

As a forensic medic, even a young one, Jiang Yuan had gradually become immune to the foul odors of crime scenes.

Standing at the scene, he took a deep breath—more out of reflection than anything else.

To be honest, this was Jiang Yuan's first time at a bloodstain scene. Though no one had died, a single glance still stirred his focus.

Level 5 bloodstain analysis—this was the first time he'd ever used it.

"Jiang Yuan, what do you see?" Wu Jun, wearing his mask, cleared his throat. He knew this was Jiang Yuan's first bloodstain scene and wanted to confirm his condition was normal.

Besides, Wu Jun also wanted to gauge Jiang Yuan's understanding of bloodstain scenes; after all, he was a newcomer to forensic medicine, and ignorance was only natural.

Jiang Yuan, asked, didn't overthink it. He scanned the scene once more to confirm his thoughts, then pointed to the pool of blood: "The victim lost a large volume of blood. A columnar trail formed on the steps in front of the house, so we can preliminarily conclude this was where the victim lay after being injured."

Wu Jun nodded. It was a basic judgment—anyone would reach the same conclusion.

Jiang Yuan took another photo with his phone and said: "The blood around the pool has dried; the center remains concentrated. Based solely on the drying pattern, the victim bled approximately four hours ago."

If this were a homicide, the time of death could be estimated the same way.

As he spoke, Jiang Yuan made simple notes on a paper notebook, to avoid forgetting later—that would be laughable. Real forensic medics had actually forgotten details like this; they'd wake up screaming at night, more terrified than seeing the victim sit up—about equally horrifying.

Wu Jun nodded again. Determining time of death had always been the core of forensic skill; every theory, every academic direction, inevitably extended toward it.

Theoretically, a forensic medic could pick up a twig at the scene and think: How can I use this to determine time of death? The remarkable part? They actually could.

Of course, the current blood pool wasn't very useful for estimating time—since the victim was still alive, and the caller reported promptly, there was virtually no doubt about the time of incident.

But for a forensic medic, every scrap of information at the scene was precious; if you could make a judgment, you had to make it.

Next, Jiang Yuan focused on the shape of the bloodstains.

In bloodstain analysis, the shape of the stain mattered more than its content.

In practice, this was true as well.

Bloodstains had a kind of time-travel effect—they were the closest thing to Sherlock Holmes's methods.

At a violent crime scene with heavy bloodshed, technicians could often reconstruct the entire event. This wasn't symbolic reconstruction—it was real: they could rebuild every motion the attacker made against the victim, even every movement the victim made before bleeding out.

At this moment, Jiang Yuan first walked to the area with spatter stains.

Spatter stains, as the name suggests, were formed when blood was projected onto a surface and then splattered outward.

If you were truly curious, try not using a toilet during bloody diarrhea but relieving yourself on the spot—the resulting bloody stool exhibits spatter characteristics.

But in bloodstain analysis, spatter stains rarely came from bloody diarrhea—everyone knew that.

They usually originated from arterial rupture and were thus considered the starting point of the attack.

So, to perform bloodstain analysis—or to become a detective who transcends time and reconstructs the scene—you must begin with spatter stains.

For Jiang Yuan, Level 5 bloodstain analysis was the perfect skill for scene reconstruction, so he went straight to the spatter stains, looked around, and couldn't help… smiling.

Because from his position, he clearly saw several drop-shaped bloodstains just beside the flowerbed, not far from the spatter.

Jiang Yuan immediately walked over.

This spot was slightly distant from the large pool of blood. The drop-shaped stains were nearly perfect circles—no tails at all…

Bloodstains with tails—like tadpoles, or longer ones resembling comets—meant one thing: the blood struck the surface at an angle. The longer the tail, the smaller the impact angle.

A bloodstain trailing a long tail, like a comet, typically struck the surface at an angle less than thirty degrees.

But the bloodstains Jiang Yuan now saw—without tails—fell vertically.

Can you imagine what scenario at a violent crime scene would produce vertical blood drops?

Only when blood dripped from a stationary person or object could such perfect circular drops form.

The victim was being hacked, his hands severed, lying in a pool of blood, gasping—how could he possibly stand still long enough to let blood drip vertically?

Besides, the volume didn't match.

So, the drop-shaped stains most likely came from the attacker.

Jiang Yuan further deduced: since the drop-shaped stains weren't continuous but just a few isolated drops, they weren't likely transferred from the victim.

In other words, the drop-shaped stains beneath his feet probably came from the attacker himself.

That was why Jiang Yuan laughed out loud.

Good thing he was wearing a mask.

Sometimes—or perhaps most of the time—crime scenes didn't require such complex reconstruction.

Jiang Yuan knelt down, carefully photographed the stains, then used a cotton swab to collect blood, wrapped it in filter paper, folded it into a triangle—his usual method. The on-site investigators had all seen it before; now they all turned their heads away.

"Young man, your eyes are sharp," Wu Jun said, walking over, impressed.

He could tell these were clearly the attacker's bloodstains—in other words, with just these few drops, the case was essentially solved.

Crimes of passion, against modern forensics, were this simple and direct.

As for why the attacker left bloodstains, that involved experience. In fact, many crime scenes showed similar patterns—basically, it came down to experience.

First-time killers or attackers often couldn't gauge how much force would recoil when they swung a blade.

Add to that the weapon was often ill-suited, and they were in a state of extreme panic, leading to improper force application and self-injury—common enough. Moreover, adrenaline masked the pain, so they overlooked cleaning up the scene.

Police always stress the importance of the primary crime scene because that's where the attacker most often leaves traces.

Serial murder cases are often solved by seeking the attacker's first murder scene, because that's where he had the least experience—and where he was most likely to slip up.

Similarly, in foreign countries, animal abuse is always monitored and recorded because it's often closely linked to violent crime and may represent an attacker's self-training.

"From these drops, what can you deduce?" Wu Jun continued testing Jiang Yuan, wanting to see if his understanding of bloodstain analysis was adequate.

Jiang Yuan looked at the other drops and said slowly: "Based on their size, the drops fell from about one meter high—likely from the tips of the attacker's fingers as his arm hung down."

"Hmm, your judgment is accurate. These drop sizes are hard to judge—there's little visible difference between one meter and one point two meters." Wu Jun shared his own experience.

Drops falling from higher up are slightly larger, but since the average person's arm hangs naturally at about one meter, drops of this size attract more attention.

Drops at one point two meters suggest the injury was higher—or the attacker was unusually tall.

With Jiang Yuan's current ability, judging drop height was effortless: "Drops falling from one meter are exactly the diameter of a Starbucks straw."

Wu Jun paused. How was a forensic medic who'd never drunk Starbucks supposed to work? But he knew the size of a one-meter drop, so he imagined the cross-section of a Starbucks straw and nodded: "So Starbucks straws are pretty thick—I thought they were all like old AD calcium milk straws."

Jiang Yuan understood: "Have someone bring Starbucks from Changyang City. We'll drink coffee while solving the case."

Wu Jun nodded in agreement and added: "Good idea. We'll drink coffee, smoke Zhonghua, and properly educate this attacker."

Just then, a detective led someone to the courtyard gate and called inside: "The victim's family has arrived."

Jiang Yuan and Wu Jun turned to see a man in his forties, following the detective, his right arm wrapped in gauze.

Both men's eyes lit up.

Wu Jun gave a subtle glance to two detectives standing nearby. When they stepped out of the courtyard and moved a few paces behind the man, Wu Jun casually asked: "How did you get injured?"

The man's voice was hoarse: "I fought the assailant and got hurt."

"This is the victim's husband. He just got bandaged at a relative's house next door," said the detective who brought him, understanding the situation. He lifted the man's injured arm as if displaying it to everyone: "Not serious—just a bit of bleeding."

Wu Jun nodded and asked: "Where did you fight?"

"Right… right there…" The man pointed to the flowerbed.

"How did you get hurt?"

"He picked up a chopping knife and swung at me—I blocked it."

"Where did you block it?"

"Right there." The man pointed again—at the flowerbed.

Wu Jun and Jiang Yuan both smiled. No spatter wounds? You really expect us to believe you blocked a blade?