He's the world's smallest prisoner.

This description refers to a highly unusual and unsettling situation. The phrase "world's smallest prisoner" suggests that this individual is extremely diminutive in stature, possibly due to a medical condition such as primordial dwarfism. Despite his small size, he is infamous for committing heinous acts, which contrasts sharply with his appearance.

The incongruity between his size and the severity of his crimes creates a disturbing image, emphasizing how appearances can be misleading when it comes to assessing a person's actions or character. The phrase also underscores the shocking nature of his offenses, highlighting that the capacity for wrongdoing is not determined by physical size but by the individual's choices and behavior.