They drive past, no graffiti.

Can they be certain? SF is a pretty compact big city with lots of graffiti. They just said that there was no graffiti on that wall. Were they 100% certain? No.

You're the only person around.

Kind of. I mean, 1am is sparse with people in general. But there are always a few people on every block walking. And as I recall, there was a line of people in the alley behind the parking lot waiting to get into a club. So there were people around in some way.

The paint should be discernably fresh and likely wet.

Meh. It was brick. Which soaks up paint pretty well.

You have paint on your fingers. It's probably the same color as the fresh paint.

Wild coincidence huh?

Maybe if they look around for 5 minutes, they even find the same can you used.

They would have found the can sitting on the roof of the building. In which case they could dust it for prints. Odd thing about my prints matching the can on the roof, is that I had just thrown it up there earlier that evening because I was bored, and wanted to throw a can of spray paint on the roof of the building. Littering charge maybe?

All your examples demonstrate is that cops frequently let insignificant crimes go because they don't give a shit about the petty stuff and they have more serious people to worry about. (And maybe because they know the licence suspension really screws things up for you.)

Well. This was San Francisco. You don't need a license. You can get anywhere by foot. So the cops weren't being thoughtful.

And believe me. They love arresting graffiti guys. I just happened to not do this graffiti that they had suspected me of. I was just walking around with a bag full of spray paint. Wink wink.