If you didn't do empty trash you can drag them out of it. Otherwise use tools like VirtualLab or data Rescure. They used to be free but not any more now.
http://www.subrosasoft.com/MacSoftware/index.php?main_page=index&cPath=1&zenid=87327fffca70641f4d95b4352ce429f8
http://www.binarybiz.com/vlab/mac.php
