So I have to tell you about my neighbors, who thought it would be fun to throw their glass bottles all over the street and in our driveway during one of their drunken parties. I got up early that Saturday morning to go to the gym, and was NOT impressed to find myself sweeping glass just to get out of my yard. We live at a 4-way stop, and there wasn't one street I could drive on that didn't have their glass all over it even AFTER I swept my own driveway. So I swept my driveway and the nearest street, but I emptied the dustpan directly behind THEIR car tires. Saw them a couple hours later cleaning it up so THEY could move, and laughed myself silly. It's been probably 3 or 4 weeks now, and guess what?! They still party ... they still break bottles ... but not in my driveway or on the street nearest me.
Maybe what you need to do - as disgusting as it sounds - is get a cheap broom and dustpan from dollarama. It should be used for nothing except sweeping up whatever they throw down on your walkway. Empty the dustpan at the foot of their stairs, or on the hood of their car ... or wait until they're asleep and put it right in front of their door. Bet you'd only have to do it once! And there is NO WAY a cop in his right mind would charge you for it. You were simply returning what was theirs in the first place.
"Life loves to be taken by the lapel and told: 'I'm with you kid. Let's go.'"
– Maya Angelou