I have several questions about the environment cards which have some condition to destroy that card.
1) If a player is incapacitated, are they unable to discard cards from their deck or hand, making it impossible to do an action that requires each player to do these things?
2) Can an incapacitated hero skip the rest of their turn to destroy a card?
3) On police backup it says "Whenever a villain card would make a player discard a card, destroy this card." Does the use of the word 'would' mean that you don't have to discard the card? (meaning police backup is destroyed instead of discarding the card).
1) The incapacitated hero would not be able to discard from hand or deck do to the fact they are no longer considered to have a deck.
2) This one is a bit more compicated. Though do to the fact they have a turn I don't see why they couldn't skip it. Maybe someone else may have a source that says otherwise.
3) Yes Police Backup would be destroyed instead of the hero discarding a card. If multiple heroes have to discard a card only one player wouldn't have to.
The other folks answered 2 & 3, but I had an additional thought on 1: I always assumed these cards meant "Active Player", as an incapacitated player doesn't have cards. Given that assumption, it resolves the confusion. That's just me, though!
Have to disagree on this - the discard is just a trigger for the Police Backup effect, as Police Backup doesn't say "instead".
An incapacitated hero skipping his turn means he wouldn't be able to use an incapacitated ability, which would give value to the thought of skipping that turn (a negative value, that is). So I see no reason why an incapacitated hero couldn't skip his turn.
As far as infection, while an incapacitated hero can be infected, an incapacitated hero cannot gain infection. Infection will only play on an active hero. If the hero is already incapacitated, Infection cannot play on him. If a hero is active, becomes infected, and then later becomes incapacitated, he maintains the previous infection.