Diary of a Criminal Investigator

At the crime scene, the deceased was lying face up on the sofa.

The wound on the neck was very clear and quite deep.

Lu Chuan was investigating over here, while Wang Hao was taking notes over there.

"The carotid artery was cut open by a sharp weapon, the wound is about 6 centimeters long and 4 centimeters deep..."

Lu Chuan pried open the deceased’s eyes: "Pupils are dilated, no clouding in the lenses, no congestion..."

At this moment, Lu Chuan had completed the investigation from the entry door to the sofa in the living room.

Some fingerprints were found as well as some footprints, all of which have been collected, but whether these fingerprints and footprints belong to the murderer is still uncertain.

Considering the investigation of the previous three cases, these footprints and fingerprints probably couldn’t identify the suspect, otherwise, the Criminal Investigation Team in Binhai City would have solved the case long ago.

Lu Chuan was now focusing on conducting a preliminary examination of the corpse.

The deceased’s cause of death was preliminarily determined to be a ruptured carotid artery, resulting in fatal hemorrhagic shock leading to death.

Feeling around the top of the head, indeed, there was something hard at the Baihui point.

Lu Chuan parted the hair to see an exposed nail cap: "A steel nail was found at the Baihui point."

Wang Hao’s hand trembled, indeed, it was still that murderer.

The first three bodies were all examined by Wang Hao and the forensic doctors from the Criminal Investigation Team of Binzhou City.

"How about this, is it the same as the nails in the heads of the previous bodies?"

Wang Hao only needed a glance to know, it was identical.

"Ordinary steel nails, 3.5 centimeters long, all new and unrusted, and we’ve found they are sold everywhere, impossible to trace the source."

"Also, looking at the shape of the wound and the blood patterns, it seems the perpetrator hammered them in after killing the victim with a hammer or another tool."

Lu Chuan agreed with this assessment.

The wound at the Baihui point did not show any stress response, indicating it was inflicted postmortem.

"Is there any difference in the wounds on the neck?"

Wang Hao stepped forward to demonstrate: "On the first victim, we found two wounds on the neck, one of which severed the carotid artery, leading to hemorrhagic shock and death, but the other did not cut through the carotid artery."

"Were they inflicted before or after death?"

"Premortem, the edges were turned outward with a distinct stress response."

"At first, we didn’t pay special attention to these two wounds, but the wounds on the second and third bodies, I and the forensic doctor made careful comparisons."

"On the second killing, he used only one cut, although the position was not very accurate, cutting only 1/3 of the carotid artery, but by the third body, the carotid artery was completely severed."

Wang Hao pointed to the fourth body beneath him: "Look at this victim’s neck wound now—a small horizontal cut and deep, showing that the perpetrator is very skilled, accurately and viciously targeting the carotid artery."

"Clearly, the perpetrator is continuously improving, becoming more proficient at killing."

Lu Chuan exhaled.

In a certain sense, killing is no different from slaughtering a chicken.

Anyone, when slaughtering a chicken for the first time, struggles to cut the neck and bleed it.

But after a few kills, the action becomes proficient, catching the chicken, drawing the knife, and bleeding it in one seamless move.

Clearly, after the culprit killed the first person in this serial case, the technique became more skilled and improved with practice.

This is the most vexing issue for all case-solving detectives.

All serial murder cases or criminals with multiple killing experiences become increasingly difficult to apprehend if not caught on the first attempt.

Over the past years, many similar cases across regions have remained unsolved.

Because during the first crime, regardless of technique or mental state, the perpetrator is highly nervous, with clumsy techniques and immature psychology, inevitably afraid of killing.

Emotional instability can cause the perpetrator to make omissions in the killing process or when handling the scene post-murder.

This is also when the police can most easily spot flaws.

But if the suspect isn’t caught during the first crime, they will likely review the whole process, adjusting any unnoticed flaws from before.

By the second crime, these flaws are mostly eliminated, and with any subsequent crimes, the methods become more and more skilled.

Fifteen years ago in the neighboring province, there was a horrific serial murder case involving eight victims.

The perpetrator’s skill level in murder reached a point where they would pass by the victim on the street, cut their throat with a hand slash,

and the entire encounter lasted less than five seconds before the murder was complete.

This type of case is nearly impossible to solve.

Wang Hao had participated in the first three cases, and he investigated all the scenes, gaining a very intuitive understanding of the murderer’s proficiency.

Lu Chuan continued with the surface examination of the body: "Three knife wounds on the abdomen, one scratch near the navel, 5 centimeters long, 1.2 centimeters deep."

"A puncture wound in the left lower back at the kidney area."

"A knife wound below the left rib, but it did not penetrate."

"The puncture wound in the kidney area and the knife wound below the left rib, with obvious outward edges, were inflicted premortem."

"However, the cut near the navel..."

The body’s physiological response to stress wounds varies in different states.

The puncture wound on the victim’s left lower back in the kidney area and the knife wound below the left rib have very obvious stress responses.

The navel scratch shows a stress response, but there is not much bleeding.

"It should be a wound left by the killer when the victim was dying..."

"Rigor mortis has not yet peaked; combined with body temperature and the clouding of the eye lenses, the time of death is preliminarily judged to be around 1:30 AM yesterday."

...

The examination of the body took the longest time; Lu Chuan continued to investigate while discussing with Wang Hao the situation of the victims from the first three cases.

"In the first three cases, we found traces of blood in the sink at the scene; we suspect the murderer cleaned the blood on their body or hands after killing."

"Did you do trace evidence analysis?"

"No, we don’t have the equipment for trace evidence testing."

Standing next to the sink, Lu Chuan opened the drain below.

Sure enough, some blood traces were found.

"The perpetrator probably wore gloves while killing and, during cleaning, whether or not they wore gloves, there might be some hair or skin flakes left from their body."

"I’ll collect some trace evidence first; the forensic team can come in next."

"Yes!"

The entire crime scene investigation continued until after 7:00 PM.

However, related results have not yet come out; the earliest time Lu Chuan projected for results was the next morning.