But even with the fingerprint, the difficulty of identification and analysis remains significant.

A fingerprint left by the same finger on a third of its surface, with blurred edges and ridges pressed together due to pressure.

It looks like five different fingerprints; this is the most challenging fingerprint Lu Chuan has encountered so far for identification and analysis.

This time, simple numerical-to-image conversion and image-to-numerical conversion can't effectively pre-process the fingerprint.

Therefore, Lu Chuan used a combination of spatial domain algorithms and frequency domain algorithms.

In image enhancement technology, frequency domain algorithms process images in a two-dimensional digital format, converting the visible 3D image into a 2D digital format.

The techniques used here are primarily basic methods like Fourier transform.

Then, through low-pass filtering, high-frequency signals are filtered out, leaving only low-frequency signals, thus removing noise interference in the image.

At the same time, high-pass filtering is used to remove low-frequency signals, as the frequency increases as the image spreads from the center to the edges.

At the very edge, the frequency is highest, and this is where the edges are the most blurred.

High-pass filtering can eliminate the influence of low-frequency signals, thereby improving clarity at the edges.

The combination of both results in some success in the spatial domain algorithm processing.

However, due to the inherent blurriness of the image, the result from frequency domain processing alone is insufficient for subsequent matching.

After half an hour of processing, Lu Chuan continued the spatial domain algorithm processing on the fingerprint image.

The so-called frequency domain algorithm Lu Chuan used involved operations on the grayscale values of the image.

This technique is divided into point operations and neighborhood enhancement operations.

First, Lu Chuan used a point operation algorithm to correct, transform, and adjust the histogram of the grayscale.

The purpose of this operation is to even out the image resolution or to expand the image's dynamic range and extend the contrast.

Then, Lu Chuan applied neighborhood enhancement algorithms to either smooth or sharpen the image.

Many high-end mobile phones on the market today actually come with functions like sharpening and adjusting grayscale values.

However, compared to Lu Chuan using professional paid software on a computer, it's like the difference between someone singing downstairs and someone firing a cannon upstairs.

The two are not on the same scale.

For every fingerprint, Lu Chuan goes through such a process.

On average, processing a fingerprint takes about an hour.

But even so, after processing, Lu Chuan still couldn't use the complete matching function of the fingerprint system.

Because the number of marked feature points wasn't sufficient.

The judicial validity of fingerprint identification is related to the proficiency of feature point matching in the fingerprint identification analysis process, and it's an absolute relationship.

With fewer than thirteen matching marked points, the fingerprint identification analysis has no legal validity.

Of course, in this situation, it doesn't mean that fingerprint identification analysis is useless.

Because as long as there are no clear dissimilarity points, it can practically corroborate the suspect's identity.

Once the other party's identity is confirmed, even without fingerprint evidence, the investigating officers can always uncover other evidence.

As long as the person can be found, everything else can be managed.

Opening the fingerprint comparison system, Lu Chuan used the system's second most common comparison method.

Similarity comparison.

Five fingerprints mean Lu Chuan has five chances.

The comparison of the first fingerprint was very unsuccessful.

The system directly gave a failed comparison.

This means that this fingerprint has dissimilarity points with all the fingerprints in the system, confirming a failed match.

The second fingerprint also failed.

In front of the computer, Lu Chuan was not discouraged. If even advanced fingerprint identification analysis skills couldn't solve this fingerprint, then there are probably very few people nationwide who could.

The third fingerprint comparison... failed once again.

He looked at the last two fingerprints that had been pre-processed, and Lu Chuan took a deep breath.

Even if all five comparisons failed, it doesn't actually mean that the fingerprint database doesn't have information on the other party.

Because these five fingerprints were severely damaged, and the fingerprint results obtained after Lu Chuan's pre-processing were significantly different.

So, if unsuccessful, Lu Chuan was already planning to pre-process the original fingerprints once again.

While thinking about this, the data of the fourth fingerprint was also entered into the system.

The pale blue halo slowly rotated in the center of the screen, and the system data had begun to match.

Beep beep beep.

Unlike the "ding" sound of a perfect match, this time the system gave continuous beeps.

Lu Chuan, invigorated, carefully looked at the screen.

Similarity match successful.

In the list, twenty-eight fingerprints lay quietly, waiting for Lu Chuan to evaluate them one by one.

"Good!"

Lu Chuan clapped his hands together, filled with enthusiasm.

Fingerprint identification analysis requires technology, and at times, it also requires luck.

Or you could call it intuition.

Having done so many fingerprint identification analyses, Lu Chuan is well aware that the feeling on the first pre-processing of fingerprints is crucial.

If the fingerprint processed on the first attempt doesn't match successfully, the distortion increases with every subsequent attempt, and the likelihood of successful matching decreases.

Of course, this doesn't mean it certainly won't match.

Persistent effort overcomes challenges; no matter how thick a copper pestle is, with enough friction, it can also be worn down.

If nothing else, at least it can be worn down to a usable state.

With the twenty-eight similar fingerprints, the system sorts them based on the number of similar feature points.

However, this doesn't mean that the fingerprint ranked first is definitely the target fingerprint, and the last rank might also be it.

The key issue is the original fingerprint was severely damaged, reduced to just a third in size, and extremely distorted.

Taking a deep breath, Lu Chuan began manually verifying from the first fingerprint in order.

This time, Lu Chuan not only compared with the pre-processed fingerprint.

The most critical comparison is with the original fingerprint as well.

This is the difficulty in manually verifying fingerprints; no matter how poor the quality of the original fingerprint is, forensic criminal analysts have to sort out and compare each ridge line one by one.

Until an obvious dissimilarity point is found, concluding a failed match.

Or if there is no dissimilarity point found, confirming it as a match.

Out of the twenty-eight fingerprints, the first fingerprint had a high similarity but was also easy to find dissimilarity points.

In less than five minutes, Lu Chuan found two obvious dissimilarity points.

After marking them, this fingerprint was bid goodbye.

Next was the second fingerprint. Lu Chuan traced along the middle ridge and went through them one by one, then compared it with the original fingerprint.

This time took even less time, finishing in three minutes.

The third fingerprint...

Two minutes.

Then the fourth, the fifth...

Like selecting beauties in a club, twenty-something predestined goddesses lined up, but who can truly soothe the lonely soul of a guest can't be judged by the manager's introduction.

Listening to him, each one possesses infinite power.

At this time, all distractions must be cast aside, starting from the beginning, choosing one by one, examining one by one.

Is the hairstyle to your liking, are the advantages prominent enough, do the eyes meet your fancy, is the dress slit just right...

Click!

When matching the nineteenth fingerprint, it was as if a bolt of lightning struck through Lu Chuan's brain.

His eyes lit up, and his mind cleared.

That feeling was akin to finding destiny, like it's the one!

For the nineteenth fingerprint, Lu Chuan meticulously compared every inch, and the entire third segment of the fingerprint was matched without finding any obvious dissimilarity points.

Of course, this doesn't confirm that the owner of this fingerprint is definitely the culprit.

After all, it is possible for one-third of a fingerprint to match someone else.

Though the probability is small, it still exists, and thus cannot be used as legal evidence to charge the other party.

However, practically speaking, identifying someone with a one-third fingerprint is usually enough to establish their identity.

And once confirmed, finding additional evidence becomes straightforward.

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