Where's the threshold of arrest?

In My Humble Opinion
1

A person breaks the law. A cop see it happen. The cop arrests the person. That’s the theory.

But the reality is that laws are being broken all the time. And most of us know that we can get away with breaking some laws some times. Even if a cop sees us do it.

You pass a police car driving five miles over the speed limit. He’s probably not going to arrest you. You shoot off some fireworks on the 4th of July. No cops will show up to arrest you. In some neighbourhoods people are openly selling drugs or sex. The cops drive through and don’t make arrests.

But if you pull out a gun and shoot somebody, you know you’re going to get arrested. Same things if you commit rape or rob a store - if you do it where a cop is watching, he will arrest you without a second thought.

So where is the line drawn? What’s the least serious crime you can commit in the presense of a cop that will always get you arrested? What’s the most serious crime you can commit in the presense of a cop that he might conceivably decide to just let slide?

2

My WAG is that the line depends on the individual cop. I once got stopped by a Fort Worth cop for driving with long hair at 2 in the morning. He followed me for blocks waiting for me to do something “wrong” so he could pull me over for it. He claimed I swerved out of my lane, which was a total lie and considering there were no other cars around for miles a ridiculous stop. He wrote up two tickets and threatened to arrest me for DUI (which was interesting since I hadn’t had a drink in weeks). Another time several years later I was stopped by Chicago cops because I didn’t have my headlights on at a time they thought I should have. They demanded to search my trunk (and I stupidly let them) and they threatened to arrest me because I had an old license plate in the trunk. They said the only reason they didn’t was because they were getting off shift and didn’t want to do the paperwork. Which are two of the reasons that I kinda hate cops.