Force empty the Trash:
At times OS X's trash can become impossible to empty. When this occurs Cocktail can force OS X to empty trash.
The SRM secure delete removes each file by overwriting, renaming, and truncating it before unlink-ing. This option meets the US Department of Defense (DOD) 5220-22M standard for securely erasing magnetic media. It erases the information used to access your files and writes over the data 7 times.