Diary of a Criminal Investigator-Chapter 354: Overlapping and Separation

Although Zhang Wang’s involvement in the gun-related case wasn’t solid, the clues provided by Sun Tao were still considered meritorious.

At the very least, a case of fake gun trafficking was cracked.

While chaos raged outside, nothing disturbed Lu Chuan in the lab.

Being able to work on a case quietly and wholeheartedly made Lu Chuan feel at ease.

Letting go of everything and focusing only on the case at hand gave Lu Chuan a unique sense of security.

However, the price of enjoying this feeling was high-intensity work.

The clearing of cold cases is something the team does every year, and even normally, someone is always keeping an eye on each cold case.

For example, in Ren Qiang’s team, each person is following up on one or two cold cases.

When there are no new cases, they follow up on the cold cases assigned to them.

Conducting investigations, reviewing documents—those sorts of things.

In short, these cases aren’t neglected just because they’re cold.

Moreover, both the team and the city bureau occasionally conduct special operations to clear cold cases.

In less busy times, they focus their efforts on tackling some cold cases.

Lu Chuan is now beginning to clear a cold case from four years ago, which is the only one from that year.

Not every year has cold cases, nor does every year involve major cases.

In Haizhou City’s Criminal Investigation Team, most cold cases are from around 20 years ago.

In particular, murder cold cases mostly concentrated in that period.

The reason is simple: the forensic technology back then was vastly different from what it is now.

Back then, there was no DNA identification analysis, fingerprint identification was just starting, and there was no fingerprint database.

During that era, DNA analysis was something only heard of abroad, and only the capital and a few economically advanced provincial capitals in China had such labs.

Everyday cases didn’t have these labs available, as they were too busy with national major cases.

Fingerprint identification wasn’t like today, where fingerprints are scanned directly into a system.

Back then, fingerprint cards were used.

Back in those days, a Criminal Investigation Team’s strength in crime scene investigation was judged by the number of fingerprint cards it had accumulated.

Of course, the police force wasn’t as finely categorized back then; there was no such distinction between frontline criminal police and crime scene investigation.

According to Liu Guodong, when he started working, Haizhou City’s Criminal Investigation Team had over 100,000 fingerprint cards.

That’s a concept that wouldn’t fit in one house.

At that time, fingerprint identification involved comparing and analyzing these fingerprint cards, looking at and comparing each one.

Wearing a magnifying glass, looking like an old sprite.

The case Lu Chuan is currently working on involves a deceased woman named Wang Huifang, who was 46 years old at the time of her death.

She was found dead in her home’s bedroom, the cause of death being a stab wound to the abdomen, leading to excessive blood loss.

The report was filed by her husband, named Zhang Chao, and the couple had no children.

When a wife dies and the husband reports it, any investigator would focus suspicion on the husband.

The Criminal Investigation Team did exactly that at the time.

However, according to the case file, Zhang Chao was at work during the time of the murder, with testimony from colleagues as evidence.

He had no opportunity to commit the crime.

Moreover, based on the neighbors’ account, the couple had a good relationship, and Zhang Chao seemed to lack a motive for murder.

Lu Chuan quickly reviewed the case file to understand the basic situation.

But this wasn’t Lu Chuan’s key focus; he was more interested in the traces left by the killer at the scene.

First, the fingerprints.

The crime scene was in the home, and the victim was killed on the bed in the bedroom; the room was full of fingerprints.

There were Zhang Chao’s, Wang Huifang’s, their parents’, and even neighbors’.

But after investigation, the various scenarios at the time were mostly ruled out.

Then there were the footprints, of which many were collected and compared with related people, including Zhang Chao, confirming they were left by acquaintances.

From the traces at the scene, the killer should have been someone familiar with Wang Huifang and frequently visited her home.

Otherwise, without the killer cleaning up the scene, some traces would definitely have been left behind.

So, who exactly is the killer?

Lu Chuan laid out the crime scene photos taken at the time on the table.

Zhang Chao’s home had two bedrooms; the couple usually slept separately, Wang Huifang in the master bedroom, and Zhang Chao in the second bedroom.

However, when Wang Huifang was killed, her body was found in the second bedroom.

No murder weapon was found at the scene, initially presumed to be a fruit knife or similar sharp object.

After studying for a while, Lu Chuan looked for an entry point to the case.

The fingerprints could be ruled out.

This crime scene was investigated by Liu Guodong, Old Bai, and Yang Sen; they had thoroughly collected the fingerprints.

And there were corresponding results for the analysis of these fingerprints.

However, since all the fingerprints belonged to acquaintances, these people would often visit even without the crime.

Hence, with no strange fingerprints discovered, it’s unrealistic to determine the killer based on fingerprints.

As for footprints, Liu Guodong’s team wasn’t particularly skilled at analyzing footprints, but basic comparisons weren’t an issue.

Footprints matched with these people, indicating no stranger’s footprints at the scene.

These two clues are very important.

If a stranger committed the crime, even if they wore gloves, they would likely leave a footprint.

But since there were no fingerprints or footprints from a stranger, it indicates the killer is one of these acquaintances.

Who could it be?

The case file detailed the investigation of these people at the time.

Unfortunately, everyone had an alibi.

The case has reached a dead end here.

Wang Huifang’s sister, parents, brother, husband, parents-in-law, and several neighbors.

A total of around ten people; the killer is likely hidden among them.

Who is it?

Lu Chuan frowned. Fingerprint analysis can identify people and even determine the subject’s recent diet based on attached oils and other substances.

But it can’t determine the order in which they were left at the scene.

Otherwise, the last appearing fingerprint owner would most likely be the killer.

What to do?

Hmm?

Fingerprints can’t show order, but footprints might!

The room is only so big; footprints can overlap.

Lu Chuan took out all the footprint photos, laid them on the table, and observed closely.

Indeed, many footprints were overlapping, one covering another.

If these layered footprints can be separated, then the most covered and prevalent footprints on top could indicate the killer’s?