Chapter 8 third chapter

The case has reached an impasse, which is something we do not want to see.I did become friends with Nancy, though, maybe because my daughter is her age.I sometimes go to see her and chat with her for a while. Nancy was obviously very willing to have me as a big friend, and sometimes told me things that made her happy or unhappy.I am still relieved to see that the shadow of losing her mother is moving away from this young girl. Today, I went to pick her up from school, planning to go home with her and have a good talk with Ed.When Nancy and I were walking on the path, she suddenly said, "Officer Pete, you know? I'm actually very afraid of walking this path."

"why?" "Because this road to school is the road my mother walked. I was very scared that there might be a villain hiding at the end of the road, and the person who committed the horrible crime might still be there, guarding the big playground. In a certain corner of the world, he will attack us on a certain night." "Don't worry, we will catch him, we will, I promise you." I can only comfort Nancy like this. I can say this because some progress has been made in the detection of the recent case, otherwise I really wouldn't be able to face Nancy's pure eyes.If there is no way to solve the case, it is impossible for me to tell lies to her.

All this, thanks to Richard Munro.He always believed that the murder weapon should be a 55-pound (about 24.9 kg) concrete slab.The slab had probably been there for five years and looked like a crash barrier used in a parking lot.He decided to conduct a field survey of the murder scene again, and one day in the middle of the night, he went alone to the murder scene in order to analyze the scene under similar circumstances to the murder. Richard stood where Shirley's body was found and thought quietly.What the hell happened here?If the victim was strangled unconscious, what happened next?When the murderer was strangling the victim, was there anyone passing by around the scene?Where did the concrete slab come from?

After numerous simulations, Richard saw a light about 500 feet (152 meters) away.In the shadows, he found a fragment of a concrete slab, and about 12 feet away, he found another. Both fragments were similar to the murder weapon, and on that dark night, this piece of light became the murderer's accomplice.If there were no lights that night, or if there were lights but the power had been cut off, then it seemed that it would not be easy for the criminals to find these concrete blocks in a short time.It was indeed the light that helped the murderer that night.Moreover, the pieces of these two pieces of concrete should have been integrated. When the criminal raised the piece of concrete and smashed it at the victim, the piece of concrete itself was also impacted by an external force and was also destroyed. After the destruction, these pieces appeared. The original whole peeled off and scattered around the corpse.

If the concrete block is strong, or if it is newly cast, then its quality must be very good. When it is rebounded by an external force, it will not even break into pieces. Now the problem is that the concrete block Fragments appear after being rebounded by external force, which shows that the quality of the concrete block itself is not the best. The ratio failed, so it became a defective product, or it could not be used in the normal parking lot as an anti-collision facility. In other words, one end of this anti-collision facility was originally standing at a place near the playground. The anti-collision facility was smashed by a car, forming such a section left on the playground.

That night, because of the light, the criminal picked up the concrete block closest to him and threw it at Shirley. When he smashed it, the criminal could clearly hit Shirley with the help of the light. any part of her to kill her. To confirm his theory, Richard needed to know whether the murder weapon and the fragments found at the school came from the same stone slab, so he conducted a geological test to compare the murder weapon with the concrete fragments found in the school playground.He found that the pattern of mix of concrete fragments and placement of small stones was the same.Because concrete has a mix ratio, that is to say, the proportion relationship between cement, water, coarse and fine aggregates, admixtures, and admixtures in concrete.

The mix ratio of concrete is usually expressed by the mass of various materials in each cubic meter of concrete, or by the ratio of the amount of various materials used.On the surface, the calculation of the concrete mix ratio is only the amount of the four constituent materials of cement, sand, gravel and water.In essence, it needs to determine the three major parameters that meet the above four basic requirements according to the conditions of the constituent materials - water-cement ratio, unit water consumption and sand rate.The amount of water consumed per ton of ash conveyed in a hydraulic ash removal system.But some people say that the water-cement ratio is the mass ratio of mixing water to cement in cement slurry, mortar, and concrete mixture.

The weathering period of concrete is 80 years, and there was a problem with the ratio of sand and cement during the casting process of this anti-collision facility, so its sturdiness will be greatly reduced. Richard believes that when a person breaks up the sand or gravel in the concrete, the entire slab breaks up and the surface becomes very irregular, with debris and small stones scattered all over the floor.To put them back together, it is not just a piece that has to be put together, but a lot of debris and small stones, which fit together as tightly as a hand and a glove. Richard suspected that the murderer might have left fingerprints on the slab, but extracting fingerprints from such a porous surface as concrete is very difficult.Porous concrete belongs to an important category of lightweight concrete, and foam concrete is the main variety of porous concrete, and it is also the variety with the best performance.

The interior of porous concrete is full of a large number of small pores, and the porosity is extremely large, generally up to 85% of the total volume of the concrete, and the density is generally between 300 and 1200 kg per cubic meter.It's like a fingerprint hiding on a pile of broken nails, the fingerprint itself is very fine, and it's hiding on something else very small. Richard tried everything he knew, including using a spray gun to spray iodine fumes, since iodine dissolves in the grease on the prints and reveals them.This method can detect fingerprints that are many months old.Iodine is relatively easy to dissolve in organic solvents, and human skin has oil stains, so when the sublimated iodine dissolves in the fingerprints, it will appear purple-black.

There are still sweat stains on the human skin, and there are chloride ions in the sweat, which will react with silver nitrate to form small particles of silver nitrate, which are black because they are small particles and not aggregates. However, Richard's experiments all failed.In the end, he turned to a method that usually picks up fingerprints on non-porous surfaces—strong adhesive fuming.The strong adhesive is made from cyanoacrylate.It is a colorless transparent liquid.Used to make instant adhesives.Its source is obtained by condensation of ethyl cyanoacetate and formaldehyde into polyethyl cyanoacrylate, and then depolymerization.Put the drop of strong adhesive and the object containing the fingerprint in a small container at the same time, and heat the container for six hours.When the strong adhesive is heated, the smoke thickens and adheres to biological material, such as the grease in a fingerprint.Under a laser, the biomaterial fluoresces, revealing a clear image of the fingerprint.

To see the fingerprints, Richard also needed to find a chemical that would bind to the cyanoacrylate.After many attempts, he finally found an effective substance, which is a biological colorant called Sudan black, which can enhance the image of fingerprints when used in trace identification. In this way, we finally extracted on the concrete slab what we were looking for, the killer's fingerprints.However, the fingerprint has been severely damaged, and the core point of the fingerprint feature is blurred. The core point is the gradual center of the fingerprint pattern, which is a reference point when reading and comparing fingerprints.Many algorithms are based on this core point, which is to process and identify fingerprints with core points.In the overall characteristics of fingerprints, there is also a triangle point, which can no longer be distinguished. The triangle point is the first bifurcation point starting from the core point, or a breakpoint, or a collection of two stripes. There are also isolated points and turning points, or points pointing to these strange and abnormal points. Therefore, we want to say that triangular points provide us with an important reference for counting and tracking fingerprint lines. In addition, the number of fingerprints of the suspect has also been indistinguishable, which is also one of the general characteristics of fingerprints.When we solve other cases, when calculating the number of fingerprints, we generally start from the point connecting the core point and the triangle point. The number of intersections between this connecting line and the fingerprint lines can be considered as the number of fingerprint lines. Also, the local characteristics of the suspect's fingerprints have been completely destroyed.We usually also refer to the node features on the fingerprint as the local features of the fingerprint, and these nodes are the feature points. When two fingerprints have overall features, the feature points of the local features cannot be exactly the same.Everyone's fingerprint lines are not smooth, straight and continuous, but often interrupted, bifurcated or discounted.These breakpoints, bifurcation points and turning points are characteristic points, which can provide us with unique confirmation information. These are all facts, but we still don't have a good solution to this fingerprint problem.Even the characteristic points of the fingerprints became blurred. It was a pity that it was caused by the environment at that time. The murderer once used the murder weapon as a pile driver and used one end of it to continuously hit Shirley's body. The 55-pound stone slab kept sliding over the perpetrator's hands.Therefore, the characteristics of fingerprints cannot be seen. Richard and I were completely stuck.We have not encountered this situation before, although both of us have studied fingerprints, and even intend to obtain the orientation, curvature and position of fingerprints from concrete.Generally speaking, the nodes of the fingerprint will face a certain direction, and we will observe the speed of change along the direction of the texture, which is the curvature. In addition, we will use coordinates to describe the position of the node.This kind of operation method relative to triangle points and feature points seems to be useless. Now we cannot verify this fingerprint which has been destroyed.Fingerprint verification is a one-to-one comparison between the fingerprints collected on the spot and the registered fingerprints. The police use this method to determine the identity of a person, but the prerequisite for verification is that the suspect's fingerprints must be in the fingerprint database. registered.Fingerprints are stored in a compressed format and linked to the suspect's name and identification.At the comparison site, first verify the identity of the suspect, and then use the fingerprints in the system to compare with the fingerprints collected on the spot to prove whether the identity matches.The principle of verification as a fingerprint identification system is actually to answer the question: "Is he who he claims to be?" So who is this said?And now we are involved in the next step, which is identification, which belongs to the principle of pattern recognition system. Richard looked at the unidentifiable fingerprint in frustration, and the plan of "one-to-many matching" was put on hold. He could only give up the plan of comparing the fingerprints collected on the spot with the fingerprints in the fingerprint library one by one.But those concrete fragments found in the school playground were crucial to the overall case.It showed that it was probably an accidental crime and that the killer was on foot.In other words, the criminal and the victim met by chance in the playground and did not know each other at first.On an August night, when you were walking alone on the large empty playground, you suddenly met someone who wanted to murder you in this situation, so the two of you started fighting together.One of them will be weak, and that weak must be a woman. A year has passed, that horrible road has gradually been forgotten, and the Ai De family seems to have finally abandoned the misfortune of the past.Nancy and her sister are now used to living without their mother.Local TV stations and newspapers reported on the still-unsolved murder, hoping to awaken some people's memories and consciences, but they didn't seem to provoke much public response. Richard and I took over other cases one after another during the year, but this question is always on our minds.But sometimes, miracles are like that, and they happen when you don't expect them. It should be said that the media reports still lead to the breakthrough that the police have been looking for. A year after Shirley was murdered, an insider in the Red Castle district denounced his roommate.He said that on the night of the incident, when the roommate returned home, his jeans and shoes had blood-like stains, and he hurriedly said he was going to take a shower as soon as he entered the room.They lived in an apartment complex across the street from the murder scene.The suspect was Mark Zamon, a 29-year-old unemployed construction worker.The whistleblower also revealed that Mark had burned his own clothes the day after the murder. This news gave me a burst of excitement.Soon, Mark's blood and saliva samples were sent to the forensic laboratory.Saliva samples differ from serum samples in that the former, a natural ultrafilter of blood, contains mainly the free (unbound) and biologically active fraction of the hormones; the latter have only 1% to 5% of the hormones in the free and biologically active state, the rest of the hormones are bound to serum proteins.In addition, salivary hormone levels, which are not affected by salivary flow rate or salivary enzymes, are excellent diagnostic indicators that measure the bioactive content of steroid hormones in the circulating blood. We use special saliva test and highly sensitive immunoassay kit for Mark saliva test.This tool is convenient, non-invasive, and stress-free for saliva sample collection.Patients can also collect samples at home or at work without the assistance or supervision of medical personnel.Tests showed Mark had type B blood, the same blood type as the saliva found on the victim's body. Photos of Mark's teeth and dental impressions were also sent for analysis.Stewart made a mold of his upper and lower teeth through the bite of Mark's teeth.Mark Zamon's teeth bite marks are clearly visible through the mold's slideshow.Mark's teeth showed obvious signs of wear, and the occlusal edges of the upper and lower teeth had been ground down.There were some peculiar gaps between his teeth and several gaps that were not repaired.After several hours of testing, Dr. Sweet found 17 coincidences between Mark's teeth and the bite marks on Shirley's body. By comparing the suspect's teeth, I can conclude that his teeth are the same as those that caused these scars.In other words, in this case, we can be sure that he was the one who caused the bite marks. In the interrogation room, when we told all this to Mark, he finally lowered his head, which had been looking very angry.He confessed that he was in the same bar as Shirley and Ed on the night of the murder, but he did not speak to them.He said he only met Shirley later near the school, when she was wandering.Mark went up to strike up a conversation, and then the two wandered to the playground to chat, and had sex on a consensual basis.Mark said he killed Shirley because Shirley threatened him that she would tell her husband what happened to them.This angered Mark, who not only emptied Shirley's wallet, but also created the illusion of robbery and murder. But how much of what Mark said was true?We don't fully trust Mark's confession. Officer Dan Rowan is a blood spatter specialist.The form of blood splatter is an important part of on-site reconstruction. When blood hits the surface of an object, different forms will be produced due to the difference in surface structure and adsorption.From the shape of the blood splatter, it is possible to infer the crime process, relevant information of the victim or the suspect, etc. The blood splatter analysis method can infer the state of the victim at the moment of blood splatter from the shape of the blood on the scene. The blood is spewed out at a speed of 20-30 liters of blood per minute according to the heartbeat frequency of the victim.If the blood is in the form of a round drop, the victim is at rest; if the blood has a "tail", the victim is being moved; if the blood is jetting, the victim's aorta is damaged.After Dan studies photos from the scene, he discovers a discrepancy with Mark's confession.If the head is hit by an object the size and weight of a concrete slab, the blood ejected from the wound can be sprayed about ten to twelve feet away and at a moderate velocity. In order to prove that his idea is correct, Ruo En conducted an experiment.A working table with an automatic device at one end, which is used to fix the end of the handle of the hammer, and then he positioned the automatic device in accordance with the requirements of medium-speed blood spurting. The experiment started, and we only saw one end of the hammer. Like a simulated human hand, it just hit down on a pre-set ball, and the inside of the ball was the injected animal blood.Then, we see blood splattered everywhere, which simulates the scene where Shirley was smashed to death with concrete blocks that night. At that time, Dan recorded the results of the experiment and compared them. At a distance of 10 to 12 feet from Shirley's body, Dan found blood spots spraying out at a moderate speed.Photos from the scene showed the contents of her purse strewn around the body, splattered with blood.This shows that Shirley's wallet was looted before she died, not after the crime. There was a fight that night between Shirley and the murderer, so objects fell to the floor, and at some point she was hit to death with something so heavy that blood splattered on the scattered objects. Dan went on to add that if the blood is ejected at a low speed, its power is relatively small. This common blood stain is mainly caused by blood dripping on the ground after a person is injured; if it is at a medium speed, it means that the force is medium. , you will see that the edge of the blood drop is not neat. In addition to the main blood drop, there will be some scattered tiny dots. Generally speaking, this kind of blood is from blows, knife wounds, sticks, hammers, etc.This is to distinguish the speed and force of blood splashing from the shape of the bloodstain and the size of the blood droplet. Mark Zamon was convicted of first-degree murder with rape and murder and was sentenced to life in prison without the possibility of parole for 25 years. Perhaps we will never learn what prompted Mark to commit such a horrific crime against that woman.If we analyze it from the perspective of psychopathy, we can only say that there are evil factors hidden in Mark's original character.On that night, after he drank, the demon was released from his heart, so when he saw Shirley alone, he finally couldn't suppress the desire in his heart, and committed such a serious crime . Another year had passed before Nancy saw me again.It was on the street and I was walking forward and she came out of a store and we said hello. Nancy told me that the criminal took Mom when she was 14 years old.She said that when her mother died, it seemed like half of her life was gone with her.But now, the murderer has been brought to justice. Although she and her two younger sisters have become motherless children, they still have a father, and the life of their family of four will continue.She also said that although she did not know how to forgive a villain who killed her mother so cruelly; although no form of punishment was imposed on the criminal, it could not make up for the pain of losing a loved one; although she said that she did not miss her mother, but she will still work hard to live happily. "I think my mother will be happy to see me like this in heaven." Nancy finally said to me. Forensic identification knowledge tips: In the case of arson, one of the main tasks of the forensic doctor when examining the burned body is to distinguish whether the deceased was burned on the spot or burned after death.The main difference between the two is that: burnt corpses can be seen with erythema, but cremated corpses are not; burnt corpses are filled with blisters, containing white blood cells and fibrin, and there is an inflammatory reaction at the bottom of the blisters and surrounding tissues, while cremated corpses There is more gas and less liquid in the pustules, and there is no inflammatory reaction at the bottom of the pustules and the surrounding area; the subcutaneous scab of the burnt corpse is congested and edematous, with leukocyte infiltration, but there is no inflammatory reaction under the scab of the cremated corpse.The internal phenomenon of the burnt corpse should be: there are soot and charcoal attached in the respiratory tract, because the living person has the ability to breathe during the process of being burned, and will inhale the soot and charcoal in the flame into the respiratory tract when breathing.In addition, incompletely burned substances in the fire site will produce a large amount of carbon monoxide, and these gases will be inhaled into the body with the breathing movement of the burned person, and combine with hemoglobin in the blood to form carboxyhemoglobin.The guts of a burned body should therefore be bright red.