Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

When the centrifuge stopped, the separated serum was a pale pink. "This color is wrong," Zhang Kai stared at the serum. "Normal serum is pale yellow. This pink color could be hemoglobinuria, indicating hemolysis—which can also occur in severe carbon monoxide poisoning, but usually only when the concentration exceeds 40%." He suddenly raised his voice, "Add cyanide testing! I suspect more than one poison!"

Xiao Lin paused for a moment, then quickened her pace: "Teacher Zhang, you mean..." "myocardial hemorrhage, necrosis of the systolic band, hemolysis," Zhang Kai's gaze swept across the dissection table, "these cannot be explained by simple carbon monoxide poisoning. The possibility of cyanide poisoning must be ruled out—that is the real killer."

Regarding the final confirmation of the time of death, Zhang Kai considered multiple indicators. The scalpel tapped gently on the tray, producing a crisp metallic sound. He picked up the ophthalmoscope; the beam of light pierced the deceased's charred eyelids, refracting a blurry halo on the corneal surface. "The corneal opacity is grade three," he said, adjusting the ophthalmoscope's focus, the lens gleaming coldly as he rotated it under his fingertip. "The pupillary area is completely blurred, appearing milky white and cloudy, making it impossible to see the iris texture and pupillary light reflex—this is a typical manifestation of corneal stroma edema; coagulative necrosis of the collagen fibers in the stroma layer leads to this opaque state."

Xiaolin's notebook already contained a corneal opacity grading chart: Grade 1 was slightly hazy, Grade 2 was cloudy, and Grade 3 was completely opaque. "Normally, Grade 3 opacity appears 24-36 hours after death," she said, measuring corneal thickness with a ruler. "However, the high temperatures generated by cremation accelerate corneal moisture evaporation and damage the barrier function of corneal endothelial cells, causing the opacity process to occur earlier." Zhang Kai put down his ophthalmoscope and gently pressed his fingertips against the deceased's eyelids: "According to the formula for corneal changes under high temperature conditions, for every 10°C increase, the rate of opacity increases by 1.5 times. The ambient temperature here reaches at least 300°C during cremation, so we need to subtract 6 hours from the baseline time, correcting it to 18-30 hours."

He turned to the rigor mortis examination, grasping the deceased's forearm with his right hand and slowly raising it to a 90-degree angle with the torso. The shoulder joint moved with almost no resistance. "Try the elbow joint," Zhang Kai said to Xiao Lin, gently bending the deceased's wrist with tweezers. The angle between the forearm and upper arm easily reached 120 degrees. "The rigor mortis has completely subsided. All the joints in the body are relaxed, even the most stubborn jaw joint can be easily opened." He used his fingers to manipulate the deceased's jaw, and the temporomandibular joint made a slight "click." "This state of complete relief usually corresponds to more than 36 hours after death at room temperature, but cremation will accelerate the relief of rigor mortis—high temperatures will destroy the binding of actin and myosin in muscle tissue, causing rigor mortis to disintegrate prematurely."

Xiaolin was recording joint range of motion data: shoulder 90 degrees, elbow 120 degrees, wrist 150 degrees—each value far exceeding the standard for the normal rigor mortis relief period. “Professor Zhang, I’ve checked the literature,” she said, flipping through a thick forensic medicine handbook. “In cremation cases, rigor mortis appears 4-6 hours later than at room temperature, but the relief time is shortened by 50%. What would normally take 36 hours to resolve might be completely relaxed in 18 hours.” Zhang Kai nodded, using a probe to brush away the charcoal dust at the deceased’s knuckles: “Look at the skin on these knuckles; it’s already leathery. This is a secondary change after rigor mortis has subsided, indicating that the relief process lasted at least 6 hours.”

The examination of livor mortis provided another important reference. Zhang Kai turned the body over; although the skin on the back was charred, faint purplish-red livor mortis marks were still visible, distributed in the shoulder blade and hip areas. "The livor mortis is diffusely distributed and does not fade at all when pressed," he said, pressing his finger on the most densely distributed area of ​​livor mortis; no pale area appeared where he pressed. "This indicates that hemoglobin has thoroughly infiltrated the tissue, which is late-stage livor mortis, usually forming 12 hours after death and reaching a stable state after 24 hours." Xiao Lin added, "However, the vasodilation caused by cremation will make the livor mortis lighter in color and wider in distribution, so it cannot be judged simply by the livor mortis at normal temperature."

Zhang Kai suddenly noticed the deceased's fingernails. The nail bed was dark purple, and there was a 0.2-centimeter gap between the nail plate and the nail bed. "The nail detachment rate is about 10%," he said, gently prying the nail plate with tweezers. "This is common in cremation cases; the high temperature causes necrosis of the nail bed tissue. However, the detachment rate is related to the time of death—within 24 hours of death, the detachment rate is usually less than 5%, and after 36 hours, it will reach more than 15%." He wrote down the value on the calculation paper: "Combined with a 10% detachment rate, the corrected time of death should be between 24 and 30 hours."

When the report on the digestion of the stomach contents arrived, Zhang Kai's brow finally relaxed. "The starch hydrolysis rate of the rice grains is 45%, and the muscle fiber breakage length of the meat fibers is about 0.5 cm," he pointed to the sample under the microscope. "This corresponds to the digestion state 4-6 hours after eating. Assuming the last meal was at 8 pm, based on the digestion time, the time of death should be between midnight and 2 am." Xiao Lin suddenly remembered something: "But high temperatures slow down gastrointestinal motility and reduce digestive enzyme activity. Shouldn't we extend the digestion time?"

“That’s right,” Zhang Kai added a correction factor to the formula. “The high temperature environment during cremation inhibits gastrointestinal function and prolongs digestion time by about 30%, so the actual time of death should be pushed back by 1-2 hours, that is, between 1 a.m. and 3 a.m..” He listed the time ranges of various indicators in a table: 18-30 hours after correction for corneal opacity, 18-24 hours after correction for rigor mortis, 12-24 hours for late livor mortis, 24-30 hours for nail detachment, and 1-3 a.m. for digestion of stomach contents. “Take the intersection of these ranges,” he circled the overlapping area with a red pen, “and finally lock the time of death to 24-30 hours after death. Based on the time the body was discovered at 6 a.m. on May 14, the time of death should be between 10 p.m. on May 12 and 2 a.m. on May 13.”

Looking at the densely packed numbers in the table, Xiaolin suddenly pointed to the rigor mortis data: "But the corrected time for complete relief of rigor mortis is 18-24 hours, which overlaps with the 24-30 hours of other indicators. Why was the upper limit ultimately chosen?" Zhang Kai picked up the deceased's femur and sawed open the cross-section with a bone saw. The bone marrow was dark red, with a small amount of fat dripping out: "The degree of fatty degeneration in the bone marrow is mild, which corresponds to the characteristics of death more than 24 hours ago. In addition, considering the digestion time of the stomach contents, an upper limit of 30 hours is more reasonable."

Zhang Kai wrote the final conclusion about the time of death on the report, his pen pausing at the words "10 PM on May 12th to 2 AM on May 13th." "Each indicator is like the hand of a clock." (End of Chapter)