Actually, some research suggests that police utilize discretion unjustly. When there are too many laws to enforce every case, police must use (you guessed it) discretion in deciding which cases to pursue.
That could involve "just" discretion, i.e. ignoring minor infractions that don't impose harm to anyone else. It could also involve unjust discretion, such as ignoring infractions by people of your own race and throwing the book at people of other races.
See for example: http://scholarship.law.duke.ed...
Oh, and F*ck Beta. (Why, you ask? Because just a week or so after Dice publishes their mea culpa, we're slowing things way down and we won't push this out because it's not ready yet... the default dns record of slashdot.org redirects to beta. Also, Beta ate this comment the first time I tried posting it.)