Did you try restarting, or shut down and restart anew?
You may have to start in safe mode, and repair disk permissions
with disk utility, to see if that helps any system files that may be
damaged. Or consider using OS X Utilities in Recovery to check
and maybe repair the hard drive.
There are several things that may need to be done. If it were
mine, I'd probably be super careful in deleting files if any chance
of removing system-owned files were to occur, as trouble results
if or when that happens. The restart may put the trash items fully
in the trash. You could also look into the health of the hard drive
to see if that may be too full or otherwise failing. In an older Mac
or any computer, a hard disk drive may wear out unexpectedly.
And an SSD may have irregularity and need some meds.
• Try safe mode if your Mac doesn't finish starting up - Apple Support
Also there likely is some method of starting up in single-user mode
or terminal and using a unix command to empty trash(es) as there
are more than one in the OS X. An admin sees one, generally.
• Mac OS X: How to start up in single-user or verbose mode - Apple Support
• About the screens you see when your Mac starts up - Apple Support
Some users have acquired OnyX utility for their version of OS X, and
carefully use some of its tools, to empty trash and perform other duties
as this can go into the lower level behind the graphic user interface. It
also can cause problems. You may be able to use OS X Utilities as part
of OS X Recovery, and straighten out some issues that way, with disk
utility. Usually an occasional simple restart can help with trash issues.
And once in awhile you may have to unlock ownership or change
permissions and the like, to get a file so it will go away. Be aware
that some files belong to the system, and should not be trashed.
In any event...
Good luck & happy computing! 🙂
