| >They were created to meet the specific law enforcement needs of each agency. Dept of Education agents investigate misuse of Dept of Education funds, That's a really charitable way of saying "handle petty stuff that the FBI can't justify spending resources on". Every specialty police department exists for this reason and this reason only. Because the mission is often so petty they wouldn't get any resources if it was obvious that resource allocation to that task was resource allocation away from other policing. When you have real problems the real police have no problems allocating resources and whipping up dedicated teams. When you feel like using state violence to harass drunken college kids you create a campus PD. When you feel like using state violence to kick the homeless out of the train station you create transit cops. Etc. etc. Even if you're an investigative agency you will have no problem getting the local cops to provide muscle if your needs are legitimate. "Look at us working with the <pick three letters>" is the kind of photo op local departments love, so long as it reflects well on them. |
Specialization is a thing within policing as much as it is within the rest of life. It's not like the same person who knows how to investigate a murder scene is equally capable of investigating complicated financial crimes on Wall St.
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In terms of aligning incentives, there are various situations where there would otherwise there would be a mismatch of "who pays for this/who's responsibility this is" vs "who this is meant to serve".
On your examples:
Campus PD - College has equal/larger population than town. Town-college relations are often tense at best. Voters in town have no interest in spending their tax money on adequate policing for the college, college has no interest in donating a bunch of money to the PD to maybe get better services that they still have no say in. Students often heavily distrust the local PD and are unlikely to report crimes to them. It's still a problematic structure, but the premise that it would be better without is questionable.
Transit Cops - No individual town or city is going to patrol the system coherently otherwise, and areas which utilize the service less are unlikely to spend significant resources policing it. Services which cross state lines also have jurisdictional issues even with just using normal state-level police.