I've seen press about police departments making such an argument, and it seems really disingenuous. The implied claim is that if no charge will be pursued by the DA then there's "no outcome" or point in doing any police work or arrest.
However, when cops feel any kind of animus, it's really apparent that they can make life awful for people by harassing, intimidating, or assaulting who aren't doing anything illegal. They understand that even if the DA will never pursue anything, being a victim of over-policing is itself a shitty position to be in. Further, it can create the basis for claims of resisting arrest. For example, in my city there's press about a woman who was physically accosted by an officer for jaywalking. There's video of an officer doing a rapid U-turn after seeing a woman walk through a crosswalk, follow her down the street and slam her int a wall. The officer claims that the woman, who was just walking down the street with headphones, disregarded his (impossible?) instruction to show him an ID without reaching into her pockets or purse.
So we supposed to believe that cops have the energy to rough up random jaywalkers (who we're pretty sure the DA isn't interested in pursuing, and which is actually legal in my state now), but not enough to pursue people doing car break-ins, mail theft, vandalism, etc because of the DA's lack of interest?
If you were a mail thief, and not a priority for the local DA (... though isn't mail theft actually a federal crime?) but the police decided that you should be picked up and detained for 1-hour less than the window at which they're obliged to release you if no charges are forthcoming, and also all the stuff you stole, and some other stuff that you didn't steal, was confiscated and you didn't get your actual property back for an indeterminate period, you might understandably reconsider the pro/con list of stealing mail, even if you never went to court.
I think the explanation for why cops don't direct their harassment power at actual criminals is not that cops are rationally not doing work that won't lead to convictions. Rather:
- police budgets increase with the severity of the perceived "crime problem". Solving problems doesn't get you more money next year.
- priorities get set by political pressures. Mail theft, package theft, car break-ins, etc have diffuse harms over a broad set of the population but not necessarily against organized political blocks. But the X Neighborhood Merchants Association that donates to the campaign fund of the incumbent supervisor can probably organize to get more policing in their area.
- policing isn't about stopping or even responding to crime; it's about being seen projecting power. Report a theft in my neighborhood, and the cops will at best take a report that you can send to your insurer. If you have video footage of the crime, no one will look at it. The won't come to the location where the crime occurred. But routinely I will see 5 cops standing around talking, with 3 cop cars blocking traffic/bike lanes/lightrail tracks, while one cop is looming over/talking at a homeless person sitting on the sidewalk. There aren't enough cops to look into serial theft, but we need all hands on deck for this one disruptive unhoused person, b/c the world needs to see how we respond when you visibly step out of line.
https://missionlocal.org/2024/08/black-woman-injured-by-sfpd...