How to delete cache file in trash?

Do you get a message that the files are in use? If so boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

The Only files that can be deleted are files that are in the User Account Folder ( Home Folder )

The Operating System resides in a Sealed and Read Only Volume that can not be opened by the User nor by Third Party Applications.

In short, move the files back to their Original Location

brodycs wrote:

Thanks.

I had tried to get into safe mode – I can see the ‘safe boot’ in upper right corner and a login.

But as soon as I put in the password to proceed, system just launches back into normal mode.

Are you sure? When you login, the words "safe boot" do not appear anymore; that is normal, and it does NOT mean that you are running in normal mode. In fact, you can't be, unless the system restarts once again.

As such, I have been unable to rid the trash of the cache.

Where were these files and folders that you want to delete? As already noted, depending on the original location, it is possible that they simply can't be deleted.