How to view drivers or items in use Mac OS X?

Instead of clicking the trash can to delete the items, have you tried clicking on ‘Finder’ in the top left & then clicking, ‘Secure Empty Trash’? See if that works in deleting the files.

Not really a direct answer to your question, but there is a program called AppDelete that is supposed to delete all the related files as well as the app itself. You can get the program here:
http://www.reggieashworth.com/

I haven’t had any problems from it. As far as I know it’s doing what it’s supposed to.

You can use Whats Open. Or you can use lsof in the Terminal.

Activity Monitor (in Utilities) shows the active processes.

If you restart, any items in the Trash that were active when you trashed them can then be deleted.

I think you might as well go with AppDelete as llewis said. Its never proved me wrong.