Mao Ji knew that Li Xiang wasn't professionally trained. He only had some fragmented knowledge from hearsay about the basic comparison of DNA data, thinking that as long as he knew the victim's DNA data, he could quickly find the victim's family through big data, even relatives from the same lineage couldn't escape under DNA comparison.

To some extent, this idea wasn't wrong, but it really just remained theoretical and didn't stem from practical experience.

There are many kinds of DNA comparison techniques. Different DNA testing methods have varying accuracy, sensitivity, and specificity, requiring the choice of an appropriate comparison method to ensure the accuracy of the results.

Comparing completely identical DNA is quick, but comparing parent-child DNA can have great errors.

To ensure accuracy, the police use dual-parent comparison.

Upon hearing Mao Ji's explanation, Li Xiang understood the basics of DNA comparison but simultaneously voiced his doubt: "What if the victim comes from a single-parent family?"

"Uh~"

Mao Ji paused, as they had always used dual-parent comparison methods for the highest accuracy, inadvertently ignoring the factor of single-parent situations.

"You're right, the victim could be from a single-parent family too, but the error margin would be larger for single-parent comparisons."

"Let's give it a try anyway, treating it like a last resort."

Li Xiang didn't understand these things and was unaware of how significant the data error for single-parent comparisons could be, but that didn't stop him from making remarks, as there weren't currently other leads anyway.

"Hmm, it's a direction worth trying. Do you have any other opinions?"

Sometimes, they tend to be fixed in this system, with investigation strategies having solidified somewhat, as predecessors have always used dual-parent comparison to confirm identities, continuing to do so without considering single-parent comparisons, which have larger errors.

Now that Li Xiang brought it up, it broke the conventional thinking patterns, refreshing everyone, so they wanted to hear any other views he might have.

"Another doubt is that the reservoir is located in a remote area, and the police suspect the murderer is local. Since the origin of the body cannot be traced, could we start investigating from the murderer?"

"The police back then also investigated, but found no leads."

Li Xiang nodded, indeed, it was hard to trace the murderer without knowing even the origin of the body.

The murderer wouldn't confess to the police just because they showed up. Without evidence, no suspect would voluntarily admit to their crimes to the authorities.

Except for those who turn themselves in, of course.

If a murderer wanted to surrender, they wouldn't have chosen to dispose of the body like this.

A day later, Cao Gang gathered everyone for another meeting about the case of the corpse sunk at Luoyang Reservoir.

"Li Xiang, have you finished reviewing the case files?"

"Yes, Captain Cao, I've finished reviewing them." Li Xiang nodded.

"Our focus going forward is to return to this case. It's been over a decade and is reviewed year after year, but I urge everyone not to be discouraged, not to think that after so many years it's unsolvable, dealing with it perfunctorily is unacceptable. Everyone must put forth 200% effort to have a chance at solving it."

Because this is an old unresolved case, with very few clues at the crime scene, the difficulty in solving the case is exponentially increased. Cao Gang also worried the case would be too complex, causing everyone to lose confidence in solving it, so every meeting, he'd encourage and motivate everyone.

"Let's re-evaluate all details of the case once more..."

Cao Gang led everyone in reviewing the entire situation of the case again, also presenting his views:

"This case's motive for murder has always been doubtful, leading to two motive theories. One is robbery murder; no valuables or mobile phones were found on the victim, suggesting the murderer robbed and killed before disposing of the body. However, skeptics argue Luoyang Reservoir is very remote, without local involvement, an outsider, especially a young girl, couldn't reach this place. Even if on a tour, it's impossible to escape locals' attention entirely."

Because according to the victim's clothing and sketch features, the police had already visited the whole village and even neighboring villages. Villagers claimed not to have seen this girl, which strengthens the evidence against the robbery murder theory.

"The opposing camp believes this might be a crime of passion, with the murderer likely being a local acquainted with Luoyang Reservoir's terrain, thus removing and disposing of the body post-murder without detection. But once again, the clue leads back to square one, as no villager has seen this girl, begging the question of whom she came to Luoyang to find, and how they knew each other."

For this case, Cao Gang racked his brain tirelessly, clinging to each emerging doubt, investigating thoroughly until a line of inquiry completely exhausted itself, then reviewing anew, discovering new doubts, investigating perennially, perpetually revising and rebuilding.

His dedication to this case was evident.

"Everyone should have a grasp of the case by now, let's brainstorm—there might be a clue emerging from the discussion."

Whenever hearing Cao Gang's views on the case and murder motive theories, Li Xiang would have a flash of inspiration, attempting to seize it each time, yet never fully capturing it, leaving him rather frustrated.

Mao Ji, upon seeing Li Xiang hadn't mentioned their single-parent theory from the previous day, decided to speak up: "Captain Cao, I think there's a good direction Li Xiang and I discussed that could be worth exploring."

"Oh? What direction?"

"Currently, identifying the victim through DNA comparison involves dual-parent confirmation for accuracy. But if the victim comes from a single-parent family, this method has its limitations, so he proposed trying single-parent comparison, which I believe can be attempted."

"Single-parent? That's a direction too, although the success rate is undetermined—as a desperate but possible method, I can instruct the tech department to try it."

Surprised by Mao Ji's words, Cao Gang again glanced at the pondering Li Xiang, as coming up with this idea indicated a flexible thought process in crime-solving.

In cases of unsolved mysteries, the fear is not the big margin of error or great difficulty, but rather the absence of clues, rendering efforts impotent.

Though single-parent comparison has lower accuracy and higher error margins, extensive comparisons can sift out highly similar data samples, each confirmed individually, significantly increasing workload exponentially.

They'd prefer not to use this method unless absolutely necessary.

"If we can identify the victim's home location, success rates will relatively increase in national system comparisons." Cao Gang pondered, and although single-parent comparison success rates are low, they can be improved by geographical stratification, filtering out many errors.

"What a paradox—we need the victim's identity to know her home location, but knowing her identity means no need for DNA comparison to confirm victim identity," Su Jiayi remarked, considering this comment redundant, as knowing the victim's home location would already clarify her identity.

"It's possible, success depends on effort - everyone, let's think."

The piece of inspiration upon hearing Captain Cao analyze the motive earlier finally formed clearly in Li Xiang's mind when hearing about the victim's home location, prompting him to say: "Actually, finding out where the victim lived isn't difficult."

While identifying the victim's precise registration might be challenging at present, discovering where she lived during her life remains possible.

"Hmm? What method do you propose?"

Hearing Li Xiang's proposal drew intrigued gazes from everyone.

It's a case suspended for over fourteen years, what solution could you have?

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