Its tricky for both sides.

A cop sees you. He starts running over. So you ditch your shit in the trash can. He can't arrest you on charges of possession, because technically there is no possession. But he can arrest you on suspicion, and if he saw you ditch your gear then he'll take it in as evidence. But then they must prove beyond reasonable doubt that the gear was yours. If they find prints, your'e screwed. If they don't, they shouldn't be able to hold you.

Can't charge you for possession.
Can't charge you for tampering with evidence (unless he can prove the gear is yours)
Can arrest on suspicion.
Can take prints.

I think in this case the cops would win.

But lets say a cop sees you. He starts running over. So you ditch your shit in the trash can but he didn't see you do it. He can't arrest you on charges of possession, because technically there is no possession. He can't arrest you on suspicion because he can't find the gear.

Can't charge you for possession.
Can't charge you for tampering with evidence - There is no evidence
Can arrest on suspicion.

Here you would win hands down.