Criminal detectives all have their little tricks.
Without needing further instruction from Jiang Yuan, Wang Chuanxing took advantage of the arrest to photograph the footprints of the two Jin Family daughters, the three daughters-in-law who arrived later, and even those of a more distantly related aunt.
Jiang Yuan just stood in the yard and watched, focusing on the gait. When he came across rather common footprints, he would take a closer look.
The gait of an individual is actually quite distinctive. For example, in families with children, when the child follows an adult and learns to walk, almost every child will imitate the adult's way of walking perfectly.
This is a special ability that children have to grasp details.
Footprints are much the same. To the average person, identifying footprints is akin to distinguishing between the faces of dogs, cats, or pigs—if there are significant differences, they stand out; otherwise, they seem vague and uncertain.