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

There are two photos of footprints. The left one was taken with a tilted lens, so the footprints are obviously stretched; the right one was taken vertically, so the length-to-width ratio is real.

In court, an error of even 1 millimeter may lead to questioning the reliability of the evidence.

Can't be careless at all.

At the same time, Yang Lin raised the survey light to shoot from the side, in order to highlight the three-dimensional sense of the traces, just like taking fingerprints.

He shone the light from the survey lamp at a 45-degree angle on the sculpture's arm.

When light passes over the surface, tiny scratches and grease residue from gloves will form a contrast between light and dark. However, the intensity of the side light must be controlled. Too strong light will cause reflections, while too weak light will not show the details.

The photo shoot ended after about half an hour.

Yang Lin half-knelt on the ground, holding a scale and labels, carefully marking the location of the traces at the scene.

"Look here." Yang Lin suddenly pointed to the pile of fallen leaves next to the sculpture base. "The fallen leaves here have obvious indentations and irregular shapes, as if someone dragged a heavy object past them."

Yang Sen half-bent his body, his tactical boots firmly stuck into the wet pile of rotten leaves, his knees making a slight clicking sound. He fumbled for a strong flashlight, and the cold white beam swept across the ground at a 45-degree angle, revealing several interlaced depressions in the pile of fallen leaves - those were irregular grooves formed by the dead leaves being crushed when heavy objects were dragged, with freshly broken leaf vein fibers still remaining on the edges.

"The dragging track is S-shaped," he moved the laser pen along the trace, and the red dot jumped on the humus, "which shows that the murderer is quite strong, but he may have encountered obstacles when moving." As he spoke, he had already put on an N95 mask and latex gloves, and the rubber made a slight friction sound when it fit against the skin. The moment the investigation box was opened, various precision instruments glowed with cold metal under the cold light.

"The adsorption film should completely cover the indentation area, and be careful not to have bubbles in the corners." Yang Sen took the electrostatic adsorption instrument handed over by Yang Lin, and the black cylindrical instrument started buzzing, releasing a fine electrostatic field. He spread the translucent adsorption film flat on the mark like a paperhanger, and pressed lightly with his fingertips through the film to ensure that every wrinkle was smoothed. "This polyvinyl chloride adsorption film can absorb all dust particles within 30 seconds."

Yang Lin stood by holding a scale, watching the changes in the adsorption film closely. The originally smooth film suddenly rippled, and countless tiny grains of sand and dead leaf debris slowly adhered to the film surface as if being pulled by an invisible hand. When the adsorption was completed, the outlines of the footprints hidden under the fallen leaves appeared miraculously - the clear sole patterns, the pressure distribution of varying depths, and even the small stones embedded in the soil were completely reproduced.

"It's amazing!" Yang Lin couldn't help but exclaim, "These marks are almost invisible to the naked eye."

"This is the magic of electrostatic adsorption." Yang Sen carefully peeled the adsorption film from the ground and put it into a special pressure-proof sealed bag. "In a dry environment, even 0.1 mm dust particles will be captured by the electrostatic field. Look at the trailing mark on the edge," he pointed to a long and thin mark on the adsorption film, "which means that when the murderer was dragging the heavy object, it was briefly stuck here, and it is very likely that he was tripped by a tree root."

When putting away the instruments, Yang Sen suddenly picked up a fiber on the edge of the adsorption membrane with tweezers: "It's made of nylon, and it's different from the one extracted from the deceased's clothes." He put the fiber into the evidence tube, and the metal box lid snapped shut with a crisp sound like knocking. "Sometimes the most inconspicuous traces hide the most crucial clues."

"I hope the fog didn't destroy the traces." Yang Lin said as he operated the instrument. "So we have to race against time." Yang Sen stared at the adsorption film, "Scan the extracted footprints into the system and compare them with the city's shoe print database. By the way, pay attention to the depth and spacing of the indentations, which can determine the approximate size and strength of the dragger."

After dealing with the footprints, the two began to extract fingerprints. Yang Sen took out a fingerprint brush and fluorescent powder and gently swept it on the surface of the sculpture: "Fingerprints are easily left on the surface of this kind of white marble. But the murderer may have worn gloves, so we have to look carefully."

"Found it!" Yang Lin suddenly shouted, "There is an unnatural reflective area on the inside of the sculpture's arm, like the grease left by a glove."

Yang Sen immediately leaned over and observed with a magnifying glass: "These are traces of nitrile gloves. This type of gloves is often used in industrial operations to protect against oil and chemicals. Take photos for evidence and mark this location."

The next step is fiber extraction. Yang Sen took out tweezers and a sealed bag and carefully searched the ground around the deceased and in the cracks of the sculptures: "The clothing fibers on the body are very important, and they may be cross-transferred with the murderer's clothing. Also, pay attention to whether there are other abnormal fibers, such as fibers from ropes and packaging materials."

"Look at this." Yang Lin picked up a black fiber from the hem of the deceased's skirt. "This fiber is thicker than ordinary clothing fibers, and has a spiral texture on the surface, like it fell off a nylon rope."

"Very good." Yang Sen put the fiber into a sealed bag and marked the information. "Nylon rope is often used for binding. It is very likely part of the murder weapon. I will do a spectral analysis when I get back and check the specific model."

When checking the nails of the deceased, Yang Lin found some skin tissue: "These tissues should be left behind when fighting with the murderer, but the amount is too small, so it may be difficult to extract DNA."

"We'll do our best," Yang Sen said. "We'll use vacuum adsorption to extract the samples to reduce damage to them. We'll also need to analyze the dirt on the soles of the deceased's shoes carefully. We may be able to find clues to the original scene."

As the on-site investigation was coming to an end, Yang Lin looked at the investigation marks all over the ground and felt a little frustrated: "It feels like the clues are very fragmented, and there is no clear direction."

Yang Sen patted him on the shoulder and said, "This is normal. On-site investigation is like putting together a puzzle, collecting every piece. Sometimes seemingly irrelevant clues may become key evidence after laboratory analysis. For example, these fibers, through chemical composition analysis, may be able to find the manufacturer and sales channel; the glove marks on the sculpture may be associated with a specific occupational group."

"But the murderer was so cautious. He wore gloves and hid the body in a sculpture. He must have come prepared." Yang Lin said with a frown.

"Because of this, he will always leave loopholes." Yang Sen sealed the last evidence bag. "There is no perfect crime. What we have to do now is to bring these clues back and let them 'speak' in the laboratory. Let's go. There are still a lot of tests and analysis work waiting for us when we return."

More than three hours later, Yang Lin and Yang Sen packed up their survey equipment and took a last look at the sculpture surrounded by the cordon. (End of this chapter)