Can't empty trash on Mac
I have faced similar problem on one of the Macs in my office.

I couldn't solve it directly, so I chose to delete the account, by backing up of all the important folders/files into another partition. Alternatively, you may move it out of the home folder to another folder (e.g. /Users/Shared/) temporarily. I deleted the user account and created a new one, which will solve problems with permissions, clear hidden data in the account and/or configuration problems like you are currently experiencing.