The file name should be a clue. There is a process that still has the file open and locked, the file won't be unlocked until the process holding the lock removes the lock or quits.
So, find out what process has locked the file and quit it, then empty the trash again.
If you're not sure what process is holding the file(s) open, you can find this out by using "lsof" via Terminal. Something such as...
$ sudo lsof +D .Trash +D /.Trashes
"Finder" having the .Trash directory open is expected, you want to find out what has files within the trash locations open.