Chapter 8: Fingerprint Comparison

The old desktop computer was operating with a creaking sound.

Hot air was blowing out of the case and dissipating into the air.

After a while, 20 fingerprints with the highest matching values were released on the right side of the LCD screen.

Jiang Yuan was not in a hurry, took a sip of tea, and clicked on the first fingerprint to look at it.

In the past two days, because of his seventeenth uncle's homicide case, the Criminal Police Team had been running at full power, and Jiang Yuan had also returned to the daily state of a forensic doctor—looking like he had nothing to do.

At the same time, he was gradually becoming proficient in the use of the newly acquired system reward, "Chongqing-style single-finger fingerprint analysis method—Arch pattern identification (lv3)".

After practicing with exercise books from his school days and public materials, Jiang Yuan decided to enter actual combat: first find an arch pattern, and then find out who it belongs to.

As the first step, Jiang Yuan chose a fingerprint collected from a robbery case in Longli County, a neighboring city.

The reason for not choosing the fingerprint of a homicide case is that under the guidance of "every homicide must be solved", homicide cases are highly valued, and resources are also very abundant. Before becoming a cold case, fingerprints have been compared repeatedly. The fingerprints of homicide cold cases that still remain in the fingerprint database are bound to be extremely difficult.

Assuming that Longli County has an unsolved homicide case and a fingerprint suspected of being the perpetrator has been extracted, this fingerprint will first be compared repeatedly by the trace examination personnel in Longli County. If the comparison fails, they will have to try to extract it again at the scene many times. In all cases where attempts are unsuccessful, they will definitely ask the municipal criminal science and technology squadron for help, or go directly to the provincial department.

If the fingerprint still fails to match at the provincial department level and the case is unsolved, then every year or two, the provincial department or even the ministry will organize special fingerprint battles to compare fingerprints involved in major cold cases. The participants are often experts from the criminal technology talent pool or youth talent pool of the provincial department or the ministry.

Jiang Yuan had already eaten LV3 egg fried rice, so for LV3 arch pattern identification, his expectations were not that strong.

Egg fried rice is delicious, but it won't glow.

It can be inferred that LV3 arch pattern identification is very powerful, but not to the point of being god-like.

Not to mention, the fingerprint databases he can compare are limited. Challenging a homicide case with the first fingerprint he gets his hands on, Jiang Yuan felt it was too easy to be frustrated.

In comparison, robbery cases are more suitable for the present.

On the one hand, ordinary robbery cases cannot reach the level of major cases in the provincial department. On the other hand, the importance of robbery cases in the county bureau is high enough, which determines that when the trace examination police collected fingerprints, they must have been serious enough. The fingerprint finally uploaded to the database has a high enough degree of correlation with the case.

That said, when Jiang Yuan clicked on the fingerprint image of the case for the first time, he was also quite surprised.

I don't know under what circumstances the fingerprint was extracted. It was blurry, and it was incomplete, only about half of a normal fingerprint. Fortunately, the fingertip part was preserved more, so there was a basis for comparison.

Besides, fingerprint deformation goes without saying.

This situation is completely different from the fingerprints left by ordinary people punching in for work. Without a little professional technology, let alone marking feature points, it is difficult to judge which finger it is.

The 20 fingerprints automatically matched by the system were all unmatched, as expected.

Jiang Yuan was not discouraged. This kind of fingerprint itself was difficult for local trace examination to match, so it was uploaded to the system. As for why the local area failed to match, it might be a technical problem, or it might be that the corresponding fingerprint was not collected in the fingerprint database.

If it is the latter, Jiang Yuan has no way, and can only look forward to the wider range of the local fingerprint database... and what he is fighting for now is the former.

For the trace examination police who do fingerprint matching, effort is a must. Only with effort is there a chance to try their luck.

Jiang Yuan closed the fingerprint comparison page, reopened the suspect's fingerprint image, and this time used Photoshop.

He carefully observed the state of the incomplete fingerprint, and then began to adjust the contrast and brightness.

Jiang Yuan adjusted it extremely meticulously, so that it took half an hour to slightly improve the clarity of the fingerprint map.

However, sharpening the knife does not delay the woodcutter. After Jiang Yuan was ready, and examined the fingerprint map carefully, the direction of the texture lines was clearer.

Immediately after, Jiang Yuan slightly adjusted the center point of the fingerprint.

Because the fingerprint is incomplete, the center point itself is uncertain. If Jiang Yuan does not adjust it, the system will automatically estimate a center point.

Jiang Yuan stared at the direction of the texture lines, repositioned the center point, then put it back into the software, changed the conditions, and pressed OK again.

Another 20 fingerprints, unmatched.

Adjust the center point slightly, compare again...

This time, Jiang Yuan took a fancy to the third-ranked fingerprint at a glance.

Ordinary people look at fingerprints, and at first glance, they all feel that they are about the same, especially those with the same arch pattern or whorl pattern, which often have to be identified with great difficulty.

But for those who have been looking at fingerprints, different fingerprint features are like freckles on an old sow's face. After looking at them for a long time, there is a sense of familiarity.

Jiang Yuan clicked on the third fingerprint directly, enlarged it and placed it on the right side of the computer screen, and then opened the original fingerprint and placed it on the left side of the screen.

The two fingerprints were put together, and the similarities were revealed without doubt.

At this time, it is not just looking at feature points, but directly judging based on the degree of similarity of fingerprints. When one-on-one, the human eye's resolution is much stronger than that of a computer.

"Matched!" Jiang Yuan muttered to himself, feeling a burst of relaxation, and submitted the matching fingerprint.

According to the rules, the fingerprint he submitted will be submitted to the experts of the provincial department. After the latter reviews it and confirms it is correct, they will click submit, and someone will notify the corresponding front-line unit, and then the local area will arrange the arrest by itself.

Of course, it is no problem for the local criminal police team to want to catch people.

Jiang Yuan couldn't care about that much, stretched, stood up to move his muscles and bones, looked at the time, and waited for work to end with peace of mind.

The life of a forensic doctor without a corpse is simple and pure.