Chapter 128 Bloodstain Analysis
As a forensic doctor, even as a young forensic doctor, Jiang Yuan gradually became immune to the unpleasant smell of the scene.
Standing at the scene, taking a deep breath, it was more of a feeling.
Speaking of which, this was Jiang Yuan's first time experiencing a bloody scene. Although no one died, Jiang Yuan felt refreshed at first glance.
This is the first time I have used LV5 blood stain analysis.
"Jiang Yuan, what did you see?" Wu Jun put on his mask and coughed. He also knew that this was Jiang Yuan's first experience with blood stains, so he had to make sure that Jiang Yuan was in a normal state.
In addition, Wu Jun also planned to see Jiang Yuan's understanding of the blood stain scene. After all, he was a newcomer to the forensic field, and it was normal for him to have things he didn't understand.
When Jiang Yuan was asked, he didn't think too much. He looked around the scene again to confirm his thoughts. Then, he pointed at the pool of blood and said: "The injured person's bleeding volume was large, and there was a column-shaped blood stain in front of the steps of the house. Therefore, initially, It can be considered that this is the position where the injured lay temporarily after being injured."
Wu Jun nodded. This was a basic judgment. It would be the same judgment method for a dead person.
Jiang Yuan took another photo with his mobile phone and said: "The blood around the blood pool has dried, and there is concentrated blood in the middle. Judging from the dryness of the blood pool alone, the injured person bled about 4 hours ago."
If this is a fatal case, the time of death can also be calculated in the same way.
While Jiang Yuan was talking, he was making simple notes in a paper notebook, so as not to make it funny if he looked back and forgot. It is true that similar things have happened to forensic doctors. It was really a nightmare in the middle of the night. It was worse than seeing the person involved sitting down. It's almost as scary as it sounds.
Wu Jun nodded again. Judgment of time of death has always been the core of forensic skills. Various theories and academic directions will automatically extend in this direction.
Theoretically, when a forensic doctor picks up a branch at the scene, he or she will think about how I can use it to determine the time of death of the deceased. The great thing is that it can really be used to determine the time of death.
Of course, the current pool of blood is not very meaningful in judging time, because the injured person is still alive, and the report of the reporter is considered positive, so there is basically no doubt about the time of the accident.
However, for forensic doctors, every bit of information at the scene is extremely rare, and those who can make a judgment must make a judgment.
Then, Jiang Yuan focused on the shape of the blood stains.
In bloodstain analysis, the shape of the bloodstain is more important than the content of the bloodstain.
In practice, this is actually the case.
Blood stains have the effect of traveling through time and space, which can be said to be the technology closest to Sherlock Holmes.
At a violent crime scene, when there is a large amount of blood, it often means that technicians can reconstruct the crime scene accordingly. This reconstruction is not a reconstruction in name only, but it can truly reconstruct every move the perpetrator made towards the victim, and even every move the victim made before she shed all her blood.
At this moment, Jiang Yuan was the first to go to the place where there was blood splatter.
Splash-like blood stains, as the name suggests, are sprayed onto objects and then spattered away.
If you are really curious, you can try not to go to the toilet when you have blood in your stool, but to deal with it on the spot. The resulting bloody stool will have a splatter-like quality.
In blood stain analysis, it is well known that splatter-like blood stains usually do not originate from blood in the stool.
It often originates from arterial blood vessel rupture and is therefore considered to be the starting point of injury.
Therefore, when doing bloodstain analysis, or if you want to travel through the barriers of time and space and reconstruct the scene like a detective, you should start with the splatter-like bloodstains.
For Jiang Yuan, LV5's bloodstain analysis is a good skill for reconstructing the scene, so he first came to the location of the splattered bloodstains, then looked around, and couldn't help but... smiled.
Because looking over from his position, he happened to see a few drops of blood, right next to the flower bed not far from the splattered blood.
Jiang Yuan immediately walked over.
This location is slightly away from the bloodstains of Dadan. The drip-shaped blood drops are almost perfect circles, with no tail at all...
A blood drop with a small tail, like a tadpole, or a blood drop with a longer tail, like a comet, all mean one thing: the blood drop fell on the surface at a certain angle. The longer the tail of the blood droplet, the smaller the angle at which it hits the surface of the object.
It is like a blood droplet dragging a long tail, like a comet. It usually hits the surface of an object at an angle of less than 30 degrees.
The blood drop without a tail, which was the blood drop Jiang Yuan was looking at, fell vertically.
It is conceivable that in a violent crime scene, under what circumstances would there be blood stains falling vertically?
It is when blood drops fall from a static person or object that they form such perfectly round drops of blood.
The victim was being chopped, his hands were broken, and he was lying in a pool of blood panting. He had no time to calm down, and then the blood dripped vertically.
Furthermore, the quantity is also different.
Therefore, the dripping blood most likely came from the murderer.
Jiang Yuan further judged that because the drops of blood were not continuous, but only a few drops, it did not look like blood stains brought from the victim.
In other words, the drops of blood at his feet probably came from the murderer himself.
Jiang Yuan laughed out loud because of this.
Fortunately, I was wearing a mask.
Sometimes, or in other words, most cases, it may not really be that complicated to reconstruct the scene.
Jiang Yuan squatted down, took a photo carefully, then took a cotton swab, dipped it in blood, wrapped the cotton swab in filter paper, and folded it into a triangle. This was his usual practice. The investigators around him had all seen it before. They all turned their heads and didn't look.
"Young man, you have good eyesight." Wu Jun walked over and said a few words with emotion.
He could also see that this was basically the blood stain left by the murderer. In other words, with these few blood drops, the eucalyptus was basically broken.
Crimes of passion, in the face of modern technology, are so simple and straightforward.
As for why the murderer left blood stains, this actually involves an empirical question. In fact, similar situations will occur in many crime scenes. A brief overview is still a matter of experience.
It is usually difficult for a murderer who kills or hacks someone for the first time to estimate how much force feedback will be caused by cutting with a knife.
In addition, the weapons used are often not handy, and the person was in an extremely nervous state at the time. It is actually very common to injure yourself due to improper application of force. Moreover, due to the effect of adrenaline, the injured person will not notice the pain, so that they neglect to clean up the scene.
Why the police always emphasize the first scene when trying to solve crimes is because it is often easy for the murderer to leave loopholes at the first scene.
When solving serial murders, why we always look for the scene of the murderer’s first murder? It’s because that’s where the murderer lacks the most experience and where he’s most likely to reveal his flaws.
Similarly, the reason why animal cruelty and killing is always paid attention to by the police and recorded in foreign countries is because it is often closely connected with violent crimes, and it is likely that a murderer is practicing self-cultivation.
"What can you tell from the blood drops?" Wu Jun continued to inspect Jiang Yuan, wanting to see if his understanding of blood stain analysis was up to standard.
Jiang Yuan lowered his head to look at the other drops of blood, and said slowly: "Judging from the size of the blood droplets, the height of the drops is about one meter. It may have been from the finger position after the murderer's arm hung down."
"Well, the judgment is quite accurate. In fact, it is not easy to judge the size of this blood drop. The difference between a blood drop of one meter and one meter and two meters is not too obvious." Wu Jun said about his experience.
The higher you go, the bigger the blood droplets will be. However, because an ordinary person's hand hangs down for about one meter, blood droplets of this size attract more attention.
A blood drop of one meter and two meters indicates that the injured part was higher, or that the murderer was unusually tall.
With Jiang Yuan's current ability, he could easily judge the height of the falling blood drop. He said easily: "The blood drop falling one meter away is exactly the cross-section size of a Starbucks straw."
Wu Jun was stunned. How could a forensic doctor who had never drank Starbucks do anything? Fortunately, he knew how big a drop of blood was from one meter, so he imagined the cross-sectional area of a Starbucks straw in his mind, and couldn't help but nodded: "The Starbucks straws are quite thick. I thought they looked like the AD calcium from before." The milk is like that.”
Jiang Yuan understood and said, "I'll ask someone to bring Starbucks from Changyang City later, and we'll have some fun while drinking coffee."
Wu Jun nodded in agreement and said: "Okay, then we will drink coffee and smoke Chinese and educate this murderer."
Just as he was talking, a criminal police officer took someone to the door of the yard and shouted inside: "The victim's family is here."
Jiang Yuan and Wu Jun looked over and saw a man in his forties following the criminal policeman, his right hand still wrapped in gauze.
The two of them couldn't help but their eyes lit up.
Wu Jun first glanced at the two criminal policemen standing next to him. After the two criminal policemen walked out of the courtyard and walked a few steps forward, when they got behind the man, Wu Jun casually asked the man, "Why are you injured?"
The man said in a hoarse voice: "I fought with the gangster and was injured."
"This is the husband of the victim. He was just bandaged at the relative's house next door." The criminal policeman who led him over understood this posture and grasped the man's injured arm as he spoke, as if to show it to everyone. Said: "The injury is not serious, there was some blood."
Wu Jun nodded and asked again: "Where are you fighting?"
"Just...just that..." The man pointed to the location, which was near the flower bed.
"Then how did you get hurt?"
"The other party picked up a hatchet and came to chop it, but I blocked it."
"Where was it blocked?"
"It's right there." The man pointed at the flower bed.
Wu Jun and Jiang Yuan both smiled, and there were no splash injuries. How dare you say that you blocked the knife?