How do you know when Donald Trump is lying?

How do you know when Donald Trump is lying?

His lips move.

I guess I should have said "wavers" or "walk back" which I presume is don't sue me speak for lie.

http://www.cnn.com/2016/03/15/politics/donald-trump-legal-fees-supporters/index.html



EDIT: a bonus quote:


"Most forms of private vice and public evil are kindled and sustained by lies. Acts of adultery and other personal betrayals, financial fraud, government corruption—even murder and genocide—generally require an additional moral defect: a willingness to lie." - Sam Harris