When I am trying to secure empty my trash, I get a dialogue box saying:
The operation can’t be completed because you don’t have permission to access some of the items."
By the sounds of it you don't ownership or read write permissions of the file(s) you are trying to delete, check in the trash, see what files are remaining.
Go to trash highlight the files the remain, press cmd + i, check the permissions, if you know the password to the admin, or the account that owns said files press the padlock in the righthand corner, and add read write permissions for your user, then try and delete again.
If you do not have access to an administrator's account, go into Terminal and type the following command:
If you're wondering what that command does, it simply "force-empties" the Trash by using the
Another way to empty the Trash is to hold down the "option" key while emptying the trash like you normally would.