Some Fourth Amendment doctrines distinguish between searches executed by police and others, being more demanding of the former. We explore these distinctions by offering a simple theory for how “police are different,” focusing on selfselection. Those most attracted to the job of policing include those who feel the most intrinsic satisfaction from facilitating the punishment of wrongdoers. Thus, we expect police to have more intensely punitive preferences, on average, than the public or other governmental actors. Some experimental evidence supports this prediction. In turn, stronger punishment preferences logically lower one’s threshold of doubt— the perceived probability of guilt at which one would search or seize a suspect. That police have a lower threshold of doubt plausibly justifies more judicial scrutiny of police searches than of nonpolice searches (as well as more-permissive rules when police perform tasks outside the scope of law enforcement). We also consider and critique Professor Bill Stuntz’s alternative explanation of the relevant doctrine.