Crime scene: 162 mystery solving puzzles to find out who the murderer is

Chapter 87 Suicidal Mistakes
One day, Detective A received a theft case. After the confessions of the people present and the analysis of Detective A, the thieves were among them, and the only clues at the scene were the footprints left by the thieves and the 200 meters outside the house. pile of sandbags. Detective A looked at the footprints, and a smile appeared on the corner of his mouth.With many years of experience in solving crimes, he said confidently: "The thief is a strong man about 30 years old." But when Detective A finished speaking, he burst into laughter, because there is sufficient evidence to prove that the thief is among them, but The strange thing is that there is neither a man in his thirties as Detective A said, nor a strong person among them.So what suicidal mistake did Detective A make?
[Answer] The prisoner can walk with the sandbag, so that the footprints left will be deeper than the original ones, which will mislead the detectives.

(End of this chapter)