If a Restart doesn't allow you to Empty the Trash...
Goto Finder > Help > type in Trash...
From Finder Help Trash...
" Empty the Trash
Empty the Trash without any warning or when it contains locked files
Hold down the Option key, and then choose Finder > Empty Trash "
Are these Files in your Trash related to Time Machine...?
Well, you can give this a try:
Open the Terminal in the Utilities folder and paste the following at the prompt:
sudo rm -Rf ~/.Trash/*
Press RETURN. Enter your admin password when prompted. It will not echo to the screen. Press RETURN again.
Again, be patient as it can take a while to remove a large number of files, so the prompt may not return right away. When it does return the Trash should be empty.