"The iron chain is tied here," Yang Qiuchi pointed to the bottom of the column, took the firewood knife and made a chopping motion, and said, "If it were you, if you wanted to use this firewood knife to cut this chain, how would you cut it?" ”

Song Yun'er took the firewood knife and looked at the column: "Of course, I used this pillar as a cushion, and pressed the iron chain on the column and cut it diagonally." ”

"Judging from this fracture, it was cut with a knife, and if you cut it according to your method, there will definitely be a cut mark on the column, or at least there will be an indentation left on the wood of the column by the iron chain that has been slashed by the wood knife. But if you take a closer look, there are only strangulation marks on the column that rub left and right, which are left by the friction of the dog pulling the iron chain when the dog is leashed, but there are no traces and indentations of the woodknife slashing. ”

Song Yun'er took a closer look: "It's just not." After thinking about it, he said, "It must have been cut directly on the ground." ”

"Take a good look at the shape of this wood knife, especially the pointed end that bends down in front, you can try it, can you cut the iron chain that is placed on the ground?"

Song Yun'er compared it and smiled: "I can't cut it, the elbow in front is supported, and the blade of the firewood knife can't cut the iron chain on the ground." After thinking about it, he said, "However, you can find a piece of wood to cushion it, isn't it?" ”

"Then look around, do you have any wood that you used as a skid?"

Song Yun'er looked around, and the yard was neat, so that she didn't see any wood used as a skid.

Yang Qiuchi said again: "Besides, isn't this pillar the best skid?" Wouldn't it be much more convenient if this person had cut a thin iron chain with a wood knife and cut it directly on the pillar? ”

That is, there were no sadds, and there were no cut marks on the pillars, so it seems that the man was not cut with a wood knife. So, what did he cut it with? ”

"It's probably an axe, so I'm going to focus my investigation on the axe." Yang Qiuchi stood up, walked back to the pile of firewood knives and axes, and instructed the yamen catchers to bring the axes back, and the remaining firewood knives were first placed in Su Lizheng's house for safekeeping, and then returned to the villagers after the matter was clarified. Subsequently, he returned to Bazhou City with a team of people.

Although the chopping tool can initially exclude the firewood knife, only the axe remains, however, there are dozens of axes brought back by the catchers, and there is no way, so they can only be tested one by one to see if they can find the axe that cut the chain.

To find out which axe cut the chain, a trace identification is required.

The axes used by the common people are generally poured from the pressure mold in the blacksmith shop, and they are poured from the same mold, so the new axe does not have too obvious individual characteristics, but after using it for a period of time, it will form its own different knife edge characteristics if it is constantly cut and polished.

The blade of the chopper is almost the same with the naked eye of the human eye, it is very sharp, as long as it is polished frequently, there will generally be no obvious curl edge, but if you observe the blade with a microscope, you can find that the knife edge is uneven, and it is precisely because of this feature that the knife cuts the object, and will leave a cutting mark on the section that is difficult to distinguish with the naked eye.

This kind of scratch looks very similar to the barcode in the supermarket, but it is generally indistinguishable and invisible to the human eye, and must be seen with a microscope. This kind of scratch mark on the cross-section of the object cut by the chopper is the same as the human fingerprint, which is very different, and there are no two cross-sectional scratches that are exactly the same.

Of course, this kind of scratch is still different from a human fingerprint. Because human fingerprints do not change throughout their lives, even if they are cut off with a knife, destroyed with sulfuric acid, or even peeled off this layer of skin. The fingerprints on the newly grown skin are still exactly the same as your original, and the striar features will not change in any way.

As long as the cutter has been polished, or often used, the original features on the knife edge will slowly disappear and change, so the cross-sectional scratches extracted by the criminal investigation department, if the cutter cannot be found within six months, under normal circumstances, this information can basically be thrown away.

This case has only happened for two days, so after analyzing and comparing the scratches on the cutting surface, we can find the chopper that formed the cutting surface.

What Yang Qiuchi has to do is to cut a certain item with the suspected chopper (usually a relatively soft aluminum rod, so that it is not easy to damage the characteristics of the knife edge of the machete), and after forming the cutting marks, compare it with the abrasion marks on the section of the iron chain extracted from the neck of the deceased.

To perform such trace comparison, a microscope must be relied upon. The microscope that Yang Qiuchi carried through is a charge-coupler microscope, which can be connected to a computer and transmit the images seen to the computer for comparison and processing.

However, the blade part of the axe has a certain length, and it is necessary to find the part of the blade that is cut and cut the chain and conduct a chopping sampling test to have comparative value.

The chemical composition of the iron chain is definitely different from that of the axe, especially the part of the steel with the knife edge of the axe, because the object action is mutual, therefore, the axe cutting the iron chain will form a scratch mark on the broken iron chain, and the iron chain will also react on the axe, which can not only cause the curl of the axe blade, but also rub part of the iron filings of the iron chain on both sides of the axe edge.

The simplest example to explain this phenomenon is to cut off a person's limbs with an axe, which will stick blood stains on the axe. Or use a knife to chop a crayon, rubbing the color of the crayon on both sides of the blade.

However, when using an ax to cut an iron chain, because the iron chain generally does not decolorize, the traces of this rubbing plane layer formed on both sides of the axe blade are generally not visible with the naked eye, so how to find it?

In modern society, it is very simple, check the chemical composition of the adhesion at the blade of each axe, and compare it with the chemical composition of the broken iron chain, and you can quickly find out which axe cut the chain, and you can accurately determine which specific part of the blade of the axe cut the chain.

If further confirmation is required, this part can be used to cut the aluminum rod to form a cutting mark, which can be compared with the fracture, as long as the extraction is timely, the same determination can generally be made. Even if the characteristics of the blade of the axe have been destroyed over a long period of time, the same determination can be made because the chemical composition of the blade adheres to the same as that of the chain fracture.

In the modern forensic physical evidence examination with chemical inspection conditions, this is very simple, but there is no chemical examination equipment in the forensic physical evidence examination equipment that Yang Qiuchi brought with him this time, because the chemical examination equipment is very different according to the different substances being tested, and it is impossible to exhaust and it is not necessary to build one.

Yang Qiuchi did not have chemical composition testing equipment in his hands, so there was no way to use this method for testing. There are only other alternatives to be found.

In what way? The top priority is to find the part of the axe that cuts the chain, and then carry out a simulation test to form a cross-sectional trace of the incision, and then do a comparative superimposition test to finally find out which axe formed the fracture.

Although the iron chain is very thin, only as thick as a silver hairpin, the iron is still relatively hard, and the hardness of the steel of the Ming Dynasty is obviously not as good as that of modern times, so the iron chain is cut with an axe, and the knife edge of the axe is likely to be curled or collapsed.

This kind of test generally uses aluminum rods, however, the Ming Dynasty is not easy to find this thing, Yang Qiuchi can only find a few thicker copper wires, copper hardness is much softer than iron, it is not easy to destroy the axe edge features.

The edge of each axe is inspected to find out the curl and chipping area, and the thick copper wire is cut with this part, and then the cross-sectional image is observed and extracted with a microscope connected to a laptop, and then the cross-sectional image is compared with the cross-sectional image of the iron chain.

Dozens of axes, each axe has almost three or five curls or collapses, cumulatively, there are hundreds to be tested, it is really very cumbersome, however, forensic examination is very boring and cumbersome, and it is even tiresome to do for a long time. But Yang Qiuchi is used to it.

I was busy until dark, and I checked a small half. In the meantime, the person sent to Huo Xiaosi's child's grandmother's house to verify the situation came back and said that Huo Xiaosi's family was indeed there the day before yesterday and had never left, and relatives and neighbors could testify.

Huo Xiaosi's family has no time to commit the crime, and it seems that they can only continue to find clues about the chopper from the broken mark.

Hong Aya came to ask Yang Qiuchi to eat a bowl of rice, and he hurriedly ate it and ran back to continue the test.

Song Yun'er asked him how he was doing, but he was only vague. None of the previous inspections found the same or similar marks as the broken iron chains, and they did an afternoon of useless work.

Song Qing felt sorry for him and asked him not to work so hard, rest well, and continue to do it tomorrow.

How could Yang Qiuchi not know that revolutionary work could not be completed, and besides, it was not revolutionary work at present. However, he is such a person, once the work starts, he does not like to stop halfway.

So, after a hurried meal, he went back to the forensic office to continue testing.

Until late at night, I was dizzy, and only half of the test was done, and the table was already full of short copper wires that had been cut and cut for testing, but I still didn't find it.

Song Yun'er came a few times, Yang Qiuchi's forensic room forbade anyone to come in, the door was tied from the inside, Song Yun'er called a few times, saying that she wanted to come in to accompany her, but in the end Yang Qiuchi still didn't open the door.

Finally, when the laptop ran out of electricity, Yang Qiuchi was dumbfounded, and he couldn't detect it, so he could only wait for the sun to come out the next day, charge it with a solar battery, and then continue testing.

――――――――――――

ps: The battle entered the last moment, and the Kangxi pigtail army surpassed the three young troops and rushed up to our position!

The forward position is in danger, and the cold light on the shining swords of the pigtail army can be seen!

What to do? What to do?!

The soldiers of the Concubine Legion are fighting bloodily, and the bright red battle flag of the Concubine Legion is still flying high on the No. 8 position!

However, the enemy has already rushed up!

It's time to test the concubine warriors! Fight! Brave concubine warriors, get on the bayonet! Blow the trumpet! The white-knuckle battle has begun!! For the sake of victory, rush!!

(To be continued)