Chapter 166 The angle of shooting
"Calculate the angle of incidence?"
Asai Narumi and Mao Lilan looked at each other, looking a little confused.
They are not wondering how to calculate the angle of incidence, but they are wondering:
"Does this still need to be calculated?"
"The gunshot wound on the deceased's head was a penetrating wound, with two bullet holes at the entrance and exit."
"As long as we connect the inlet and outlet, can't we determine the trajectory of the bullet and the angle at which it enters?"
Two points confirm a straight line. This is a very simple principle.
And since the trajectory of the bullet when it passes through the human body can be confirmed, the angle of entry of the bullet can be estimated by simply measuring the angle between this straight line and the human body surface.
With this idea in mind, while raising doubts in their hearts, they unconsciously approached the corpse and observed the wounds on the corpse's head:
"The bullet hole in the forehead was the entry point."
"The bullet hole in the back of the head is the exit port."
"Is that right?"
Before estimating the shot, Mao Lilan and Asai Narumi asked Lin Xinyi with some uncertainty.
One of them is a new apprentice, and the other has just changed his career as a forensic doctor. Neither of them is good at examining injuries, especially gunshot wounds that are rarely encountered in daily life.
Nowadays, the injection entrance and exit can be determined mainly based on the splatter-like blood stains on the glass window behind the deceased, and indirectly confirmed through spatial restoration and imagination.
"Yes." Lin Xin nodded, confirming from the perspective of wound characteristics:
"The injection port is a wound formed by the bullet hitting, squeezing, and shearing the skin. It is generally similar to or slightly smaller than the diameter of the bullet, and is accompanied by a skin defect in the center of the wound. The edges of the defect appear to be involuted, making the entire wound resemble a whirlpool funnel shape. ."
"The injection port is the wound caused by the bullet piercing the skin tissue. The diameter of the injection port is generally larger than the injection port, and it is accompanied by skin tears at the wound."
"The traumatic characteristics of the two are relatively easy to distinguish, and there is no mistaking them."
He replied in the affirmative.
Then, before Mao Lilan and Asai Narumi continued to ask questions, Lin Xinyi said:
"I know what you mean."
"Looking at the position of the entrance and exit of light:"
"The injection port on the forehead is only slightly higher than the injection port on the back of the head."
"If you simply connect two points into a straight line and confirm the 'creation path' through this method, the estimated injection angle will be hmm."
Lin Xinyi didn't take any measurements, he just estimated casually through visual inspection:
"It's about 70 or 80 degrees. It's a rather blunt angle."
"That's right."
Asai Narumi nodded and expressed his thoughts:
"Since the bullet was shot from high to low at an obtuse angle, it entered the brain of the deceased."
"As long as the murderer is tall enough and holds the gun slightly higher than the deceased's head, such a wound can be caused."
As he spoke, Asai Narumi simulated the appearance of the victim based on his imagination.
He pretended to be forced to the wall by the murderer, leaning against the wall and slightly bending his knees to lower his height appropriately.
Mao Lilan, who was wearing a pair of high heels and had an advantage in height, walked up to Asai tacitly and cooperated to play the role of the murderer.
She raised a "pistol" that didn't exist at all, and pointed the "muzzle" at Asai Narumi's forehead in a condescending manner.
"Pa!"
Mao Lilan acted so devotedly that she even dubbed the voice unconsciously.
After "shooting Asai to death", she turned her head and said to Lin Xinyi:
"Mr. Lin, look."
"The height of my gun is only slightly higher than Dr. Asai's head."
"When shooting, the bullet is fired from high to low, which naturally forms a blunt angle of entry similar to that on the head of the deceased."
"In this case."
"The murderer's shooting posture can't be said to be 'strange', right?"
She expressed her doubts with some concern.
But Lin Xinyi shook his head gently:
"No, you are mistaken."
"You made this judgment based on the fact that the angle of incidence was relatively blunt."
"And you were sure that the angle of entry was blunt, and you simply connected the entry and exit points with two points to estimate the angle between the bullet's path and the human body surface."
"This" Mao Lilan was slightly startled: "Mr. Lin, what do you mean?"
"Is the angle of incidence determined simply by the positions of the injection inlet and outlet actually wrong?"
"No, that's true most of the time."
"After all, it is true that two points confirm a straight line."
"But we have to analyze specific issues in detail."
Lin Xinyi paused for a moment and explained in detail:
"And the question now is:"
"The path created by the bullet after it enters the human body is sometimes not a straight line."
"First of all, as the flight distance of the warhead increases, the flight attitude will become less stable."
"Secondly, the warhead encounters resistance when it hits the human body and sometimes changes its direction."
"Especially in this case. The deceased was hit on the frontal bone, which is almost the hardest bone in the human body."
"Therefore, the path created by the bullet when it passes through the human body is not necessarily a straight line. Curves or even broken lines may appear."
"This can have a big impact on the shooting angle."
"Especially making judgments based solely on the straight-line connections between entrances and exits is prone to huge deviations."
He explained it carefully, causing both Mao Lilan and Asai Narumi to react:
"I see."
"Since the path may not be a straight line, the method of confirming the straight line with two points and then estimating the angle of incidence cannot be applied here."
"So, how to determine the angle of incidence in this case?"
Both of them blinked their big watery eyes, full of curiosity.
Lin Xinyi continued to explain:
"It's simple, I said it before."
"If the warhead enters the human body at an angle, an oval-shaped skin defect will form at the entrance."
"The sharper the angle of incidence, the flatter the elliptical shape formed."
“It was only when I saw that the shape of the skin defect at the injection port was too ‘elliptical’ that I felt there was something wrong with the angle of injection.”
"And it's very easy to calculate the angle."
"Measure the long axis length X and short axis length Y of the oval wound."
"Then Sinα=Y/X, α is the angle of incidence."
This is a sine calculation method that uses the relationship between the diameter difference of the injection port and the impact angle to infer. Anyone who has studied junior high school mathematics can understand it.
Mao Lilan and Asai Chengmi quickly understood this method, and followed Lin Xinyi's instructions to carefully measure the major axis and minor axis of the injection port with a ruler.
Through calculation, it was found that it was different from the originally estimated 7 and 80 degrees.
"The angle of incidence is only about 45 degrees."
"Shooting from high to low, at a 45-degree angle to the surface of the human body."
Asai Narumi imagined it for a moment:
"Did the murderer raise the gun high above his head and then shoot downward?"
"Or did you jump up before shooting and then shoot down?"
He imagined several shooting postures of the murderer, and the images that came to mind were no different from performing acrobatics.
However, Mao Lilan thought of a more reliable reason:
"Could it be that the deceased lowered his head or crouched down when he was shot?"
"This is unlikely." Lin Xinyi shook his head:
"Because after the bullet penetrated the back of the head, it quickly penetrated the glass window."
"The bullets are shot from high to low as a whole, which can be determined from the positions of the exit and entrance."
"In this case, the height of the bullet hole at the injection port must be higher than the height of the bullet hole in the glass window."
"And I just measured it with a tape measure when I did the autopsy."
"The height of the bullet hole on the glass window was only a few centimeters lower than the height of the deceased."
"If he had crouched down or even lowered his head a little, the bullet would not have been able to reach the height of the glass window after it pierced his brain."
"So, the deceased could only stand upright in front of the glass window when he was shot."
Hearing this, Mao Lilan couldn't help but fell into deep thought.
She carefully observed the bullet holes in the glass window, simulating in her mind the strange scene of the bullet entering the forehead at a 45-degree angle from top to bottom, then going through the head of the deceased, and then penetrating the glass backwards.
The more I think about this scene, the more awkward it becomes.
If the deceased was really standing straight in front of the glass window, then according to this angle of incidence, the murderer would have to fly to the ceiling and shoot.
"etc."
Mao Lilan's tightly frowned brow suddenly relaxed:
"We have been using this glass window with splattered blood stains as a reference to speculate on the deceased's position."
"Because the glass window is now closed vertically, Mr. Lin, you speculate that the deceased must have been standing upright in front of the glass window at that time."
"But... this glass window was not necessarily closed at the time!"
"After all, if the deceased slumped against the window after death - the window that was originally open would probably close on its own as the body slid down against the window."
Mao Lilan looked at the tightly closed glass window and murmured.
"It doesn't have to be closed."
Lin Xin suddenly realized something:
This window is not an ordinary left-right sliding glass window, but a relatively rare up-and-down opening and closing glass window.
Once opened, the angle between the glass plane and the ground will tilt.
Thinking of this, he tried to push the flip-up glass window outward.
The glass window tilts and flips, with the upper half facing outwards and the lower half facing inwards.
"Could it be."
"The scene we just imagined and restored was all wrong?"
Under Mao Lilan's reminder, Lin Xinyi found a completely different direction of analysis.
He poked his head out of the open glass window and looked up naturally:
"This shot may not have been fired in this room at all."
"It's coming from upstairs, vertically downward."