You can delete locked files in the Trash by holding down OPTION while emptying the trash, but this may not help your situation.
Have you tried moving all the trashed items to a new folder, and doing an "sudo rm -rf <new-folder>" of that folder?
NB: This is a very dangerous command if used incorrectly - it will delete anything with all authority, no questions asked, with no option for recovery. make sure you delete only the items you don't want.