Chapter 755: Chapter 404: Bringing Up the "Willow Leaf Blade" Again!_2

"Every step of the operation, every discovery, must be based on meticulous observation and scientific methods."

After a brief pause, He extended his hand and said, "Give me two cotton swabs."

The assistant quickly handed over ordinary cotton swabs, but Jiang An supplemented, "Make sure they’re sterile."

He continued to explain to everyone, "Our current task is to confirm as much as possible whether the deceased was violated before death."

"Ideally, the location for evidence extraction is the mucous membrane of the vulva, but that area is now severely charred and cannot be effectively examined."

"While the uterus still has residues, particularly if certain biological components remain in the cervix or deep in the uterine cavity—such as DNA in silent residues—that would be highly valuable for identification."

Zhang Yean nodded in agreement, her expression becoming equally serious, "Indeed, if we can extract relevant biological traces from here, it would undoubtedly greatly push the case forward, even directly related to conviction."

"Such physical evidence is often more reliable than confessions or circumstantial evidence."

In fact, this has been Jiang An’s focus since taking over the case.

Finding the suspect is important, but accurately and scientifically proving their crime is often the key to solving the case.

Fire represents warmth and light, but it can also be an accomplice to destruction and cover-up; many pieces of evidence are damaged or even vanished.

At this moment, Jiang An, while organizing his laboratory records, continued calmly, "Details often determine success or failure, particularly in forensic examinations."

"Go get the PSA from the reagent cabinet."

"PSA? What’s that?"

A young assistant looked up, asking curiously.

She had just been transferred to the lab and was unfamiliar with some technical terms.

Jiang An turned around, patiently and clearly explaining, "PSA stands for ’Prostate-Specific Antigen Test Kit.’"

"We use this reagent to test samples from a woman’s lower body, primarily for preliminary screening to determine if she was violated before death."

"Its principle is to detect whether the sample contains prostate-specific antigen, which typically originates from semen."

While speaking, Zhang Yean had already turned to the reagent cabinet, skillfully retrieving a sealed test kit.

Next, she efficiently opened the package, taking out a small bottle of transparent solution and a white test strip.

Jiang An used the cotton swab with the previously collected sample to stir in the bottle’s liquid several times to ensure the sample was fully dissolved.

Then, glancing at the clock on the wall, he calmly said, "Wait 10 minutes."

The laboratory was silent, with only the faint sounds of the instruments operating.

As time passed minute by minute, everyone held their breath, occasionally glancing at the test strip gradually reacting.

After 10 minutes, Zhang Yean gently picked up the test strip, and everyone quickly gathered around—two distinct red lines were clearly visible on the strip, indicating a positive reaction.

Zhang Yean couldn’t help but exclaim, "Positive!"

Although He was not a professional forensic expert, He was very familiar with the significance of such basic testing through years of criminal investigation work.

The results indicated that the sample indeed contained prostate-specific antigen.

Jiang An nodded, responding with a serious expression, "This means there are male biological elements in the deceased’s body."

"Next, we will conduct further confirmatory tests for sperm and DNA extraction from uterine contents."

"Once STR typing is successfully extracted, the case will make significant progress."

He paused, adding with a deeper tone, "Such biological evidence can often directly point to the suspect, even becoming key in identifying the real culprit."

Meanwhile, Wan and Qin Feng were leading the special investigation team members, driving to the school where the deceased, Zhang Qian, had studied, to conduct thorough external investigation work.

As the police car entered the school’s gate, it was recess time, the noise of students scattered around the campus in stark contrast to the solemn atmosphere inside the car.

Upon arriving at the school’s administration office, Wan proactively showed his badge to the person in charge, speaking with a steady and clear tone, "Hello, Mr. Li, we are police officers from Jiangcheng Criminal Investigation Brigade, currently handling a criminal case and need to learn some related information from your school. We ask for your cooperation."

Mr. Li quickly stood up to welcome them, appearing slightly anxious but cooperative in attitude, "Please come in, officers. Please come in!"

"We will do our utmost to assist in the case. Feel free to ask any questions."

Wan gestured lightly, maintaining a rigorous yet gentle attitude, "No need to be nervous!"

"We mainly want to learn about the student Zhang Qian."

"This incident has caused great distress to all the teachers in the school."

He paused, his tone growing heavier, "Though the child’s academic performance wasn’t particularly outstanding, her character was normally quite docile and quiet. How could she encounter such misfortune... We will fully cooperate with the police’s work, hoping to bring the murderer to justice soon!"

Wan solemnly nodded in response, "Thank you for your understanding and support."

"Could you please bother to have her homeroom teacher and several teachers who know her well to come over?"

While pouring tea for the officers, Mr. Li sighed, "This child Zhang Qian... is truly pitiful."

After 10 minutes, a middle-aged woman with a cultivated appearance and metal-frame glasses knocked on the administration office door.

As she entered, she showed a trace of doubt and unease on her face.

Upon seeing her, Mr. Li quickly arose, introducing her to the officers, "This is Zhang Qian’s homeroom teacher, Li Jia."

"Mr. Li has been with this class for over two years and is very familiar with the students’ circumstances."

"Hello, Mr. Li."

Wan and Qin Feng immediately stood up, Wan presenting his badge once more.

"We’re here today to gain detailed insight into Zhang Qian’s performance during school hours and hope to receive your active cooperation."

Mr. Li lightly nodded, her expression solemn as she sat on the chair opposite the officers, her hands inadvertently resting on her knees.

"Rest assured, officers. I’m Zhang Qian’s homeroom teacher and know her fairly well."

"I’ll certainly provide all the information I’m aware of."

Wan opened the notebook he carried with him, ready to meticulously record the conversation.

"Could you tell us about Zhang Qian’s general behavior at school, including her academic performance, personality traits, interpersonal relationships, and so on?"

Mr. Li thought for a moment before responding, "Zhang Qian’s performance in class has been consistently at a mid-level, not particularly outstanding, but her attitude towards learning has always been serious and steadfast."

"Her personality is quite quiet and introverted, not speaking much, but she gets along well with her classmates, rarely having conflicts or disputes."

She paused, her tone becoming somewhat heavy, "Our school regularly holds mental health lectures and thematic class meetings, and I often use extracurricular time to engage in individual exchanges with the students."

"In my impression, Zhang Qian is intrinsically a kind-hearted, gentle girl."

"It’s very difficult to imagine... she would encounter such a tragedy."

Saying this, she couldn’t help but shake her head, with a look of deep regret and puzzlement in her eyes.

Wan and Qin Feng exchanged a meaningful look, and then pursued further, "During school hours, did Zhang Qian show any signs of being in a romantic relationship?"

"Or exhibit any close interactions with male classmates?"

"Romantic relationship? Probably not."

Mr. Li replied affirmatively, "Although our school doesn’t explicitly prohibit student interactions, we always stress that the focus in junior high should be on studies."

"We’ve been guiding students to prioritize their efforts on learning."

She adjusted her sitting position slightly, continuing, "From my usual observations and understanding, she probably doesn’t have closely bonded male friends at school."

Wan keenly pursued, "What about outside of school?"

"Could she potentially be involved through online social platforms, or have relatively familiar male friends outside school? Are you aware of any such aspects?"

Upon hearing this question, Mr. Li inadvertently spread her hands, her tone becoming somewhat hesitant.

"This... honestly, we have very limited grasp of the students’ situations outside school."

"Zhang Qian is a day student, leaving school every day after classes."

"Regarding the online relationship you mentioned, I haven’t heard any related rumors, nor have we received parental feedback in this regard."

As she spoke, her eyes showed some evasion, not directly meeting the officers’ gaze.

This subtle movement did not elude Wan’s keen observation.

He leaned slightly forward, speaking with sincerity and gravity, "Mr. Li, the nature of this case is very serious, shocking and heartbreaking for us all, including you."

"To uncover the truth as soon as possible, we urge you to speak plainly, holding nothing back."