I'm afraid that any time you operate a helicopter, you have to assume the responsibility for the downwash - it simply goes with the territory. The same responsibility extends to the appropriateness of a landing area.
To find yourself in that situation relies only one thing - your own decisions. If you're blowing away all the
furniture, you're in entirely the WRONG place for a helicopter.
Don't have much sympathy for anyone who creates a situation like this, whether it be at an airport, or a landing area. Responsibility comes with priveleges of operation. Instances like this, are why it there are more restrictions all the time on landing areas.
Don't know that there is anything gained by a prosecution though?
I've seen a lot of stuff destroyed by helicopters, including being blown off my feet as well (bit bigger ship than a twin-star, bit more than 6 stone)!
I once had a 1000 pound main rotor blade in a box, blown over the side of a barge into the sea by downwash! <img src="eek.gif" border="0">