eurekapd Chapter 943 Forensic Identification, Identity of the Remains
Chapter 943 Forensic Identification, Identity of the Remains
In fact, there are multiple methods in forensic medicine for determining male and female sex through skeletal remains.
The pelvis is one of the most important skeletal structures for distinguishing males from females.
Generally, the male pelvis is more robust and heavy. The pubic symphysis is relatively narrow and long, and the pubic arch angle is small, usually less than 90°, forming a "V" shape. The ischial tuberosities are prominent, and the greater sciatic notch is narrow and deep, forming a "U" shape. The acetabulum is large and deep, and the pelvic cavity is funnel-shaped, with a heart-shaped upper opening and a narrower lower opening.
The female pelvis is relatively delicate and slender. The pubic symphysis is wide and short, with a relatively large pubic arch angle, generally between 90° and 100°, forming a "W" shape. The ischial tuberosities are relatively small, and the greater ischial notch is wide and shallow, forming a "U" or nearly "V" shape. The acetabulum is small and shallow, and the pelvic cavity is cylindrical, with an approximately circular upper opening and a wider lower opening, facilitating fetal delivery.
In addition, features of the skull can also provide some clues for gender determination.
Male skulls are generally larger and thicker, with rougher bone surfaces and more prominent muscle ridges. The forehead is more sloping, the brow ridges are prominent, the eye sockets are square, the nasal bones are wider, the cheekbones are more robust, and the mandible is broad and thick with a blunt angle, generally less than 120°.
Women's skulls are relatively small and thin, with smooth bone surfaces and less prominent muscle ridges. The forehead is more vertical, the brow ridges are not prominent, the eye sockets are round, the nasal bones are narrower, the cheekbones are relatively slender, and the mandible is narrower with a sharper angle, usually greater than 120°.
In addition to these differences, there are also some differences in the limb bones between the sexes. Male limb bones are generally thicker and stronger, with thicker cortical bone, more prominent muscle attachment points, and larger articular surfaces. For example, the femur and humerus are relatively longer, thicker, and have larger medullary cavities.
Women's limbs are relatively slender and delicate, with thinner bone compaction, less obvious muscle attachment points, and smaller articular surfaces. The femur and humerus are relatively shorter, with thinner bone bodies and smaller medullary cavities.
By comprehensively analyzing the skeletal characteristics of the remains, Zhang Lin can determine the sex of the skeleton with relatively high accuracy.
Of course, these characteristics are not absolute, and there may be certain differences between individuals. Therefore, in actual identification, it is necessary to combine multiple characteristics for comprehensive analysis.
However, based on the skeleton discovered so far, there shouldn't be much of a problem in determining its gender.
After determining the sex of the skeleton, the next step is to determine its age.
Age determination is a complex process, and Zhang Lin used multiple methods. "First, I observed the pubic symphysis surface. Its morphological characteristics showed a ridge in the middle of the symphysis surface, obvious grooves on both sides, and a certain degree of osteoporosis, which is consistent with the characteristics of an age group of 35-45 years old." He then picked up a magnifying glass and carefully examined the skull. "The degree of healing of the cranial sutures can also be used as a reference. The anterior two-thirds of the sagittal suture has healed, and the coronal suture is partially healed. Based on the combined assessment, the age is around 40 years old."
The degree of tooth wear provides an important supplement to age determination. Zhang Lin removed the mandible and observed it under a microscope: "The occlusal surface of the teeth is severely worn, the dentin is exposed, and the enamel is almost worn smooth. According to the tooth wear grading standard, it reaches level five wear, which also supports the judgment that the age is around 40 years old."
After determining the basic information, Zhang Lin began to estimate the time of death. "Based on the degree of fossilization of the bones, the bone color is grayish-white, and the hardness has increased. Combined with the local soil environment and climate conditions, I estimate that the time of death is between 10 and 20 years ago." He then took some bone samples for radiocarbon dating, "waiting for the test results to determine the time of death more accurately."
During the examination of the remains, Zhang Lin discovered a gold ring on the ring finger of the deceased's left hand. The ring was covered in dirt and grime, but the delicate patterns were still visible. "We will extract the ring for forensic analysis to check for any engravings or other special markings," he said. He carefully removed the ring and placed it in an evidence bag, "while also wiping the surface of the ring to extract any possible DNA information."
Finally, regarding the determination of the cause of death, Zhang Lin focused on examining the depression on the skull. "An irregular depressed fracture was visible on the right parietal bone of the skull, with the fracture line radiating outwards and irregular edges, consistent with the characteristics of blunt force trauma." He used a 3D scanner to scan and model the skull. "The depression is 1.5 cm deep, sufficient to damage brain tissue and cause intracranial hemorrhage. The cause of death is presumed to be a blunt force trauma to the head, resulting in severe craniocerebral injury."
After all the testing steps were completed, Zhang Lin began extracting DNA from the remains. He selected the proximal femur, which had a relatively high DNA content, cut it open with a bone saw, and extracted the bone marrow tissue. "We used the phenol-chloroform method to extract DNA, removed impurities, performed PCR amplification, and established STR typing." Zhang Lin placed the extracted DNA sample into the testing instrument, "waiting for the test results to come out, comparing them with the missing persons database to confirm the identity of the deceased."
The clock in the dissection room pointed to two in the morning. Zhang Lin took off his goggles and rubbed his sore eyes.
The forensic work is basically complete.
The next morning, an unexpected event occurred.
When the DNA comparison results showed that the remains did not match Wang Jianjun's immediate family, an eerie silence fell over the Criminal Investigation Division's conference room. The blue light from the projector flickered on Li Ming's face, and the conclusion on the screen, "Excluding parentage," stung the eyes. Zhang Lin slammed the test report heavily on the table, the pages rustling as they fell: "The mitochondrial DNA and Y chromosome data don't match at all. This skeleton is not Wang Jianjun."
Old accountant Chen Shufen clutched her faded work badge, veins bulging on the back of her hand: "Impossible! The work badge, the warehouse manager's identity, the time of disappearance—everything matches up. He was wearing this blue work uniform before he disappeared..."
After the case reached a stalemate, Li Ming readjusted the direction of the investigation.
Only by confirming the identity of the remains can we investigate the specific details of the case from back then by examining the relationships between the deceased and others. From an investigative perspective, only after the identity of the remains is confirmed can there be any further progress. Because this case happened so long ago, no one knows exactly what happened back then, and there were no valuable clues left on the remains.
As for Wang Jianjun's disappearance, it's not necessarily related to this case at present. It will definitely be put aside for now, because the investigation into Wang Jianjun's 10+ yuan was conducted back then, but without much progress.
Missing persons cases are not the same as murder cases. Missing does not necessarily mean that a person is dead; there are many possible scenarios after a person goes missing.
Only after death is confirmed can a case be investigated, so there are principles and procedures for handling such cases.
After focusing on confirming the identity of the remains, Li Ming personally led his team back into the old textile factory's outpost. The old archive room was filled with a damp and musty smell, and thick dust was piled up on rows of iron shelves.