I THINK I HAVE SOLVED THIS.
I seems to be a caching issue. I did a full automation using the Onyx App. Although I did the full thing, leaving out only the Spotlight reset, I believe it was ultimately the clearing of the caches which broke the link that caused my error -8003. So I could finally empty the Trash.
I wouldn't be brave enough to use Trash It. I don't know enough about the App and am very cautious about using weird Apps.
I used the trusty old Onyx. Clear your caches. Try Empty Trash again.
P.S. Secure Empty Trash didn't work for me. Use Onyx, select the Automation tab > check all the "Cleaning" checkboxes. If it doesn't work for you you can go back to check all the checkboxes - even ones not in the Cleaning section. But I don't think you'll need to go this far. There is no need to reset Spotlight, so you can leave that one unchecked.
P.P.S iCab was the App that caused this issue for me. That App is never getting back on my machine.
P.P.P.S Never touch the App iClock with a ten foot barge pole. iClock had nothing to do with this issue, but I just thought I'd warn you all. If you think it's tough deleting iCab, iClock is a vicious worm of an App that infests your Mac like poison Ivy.