exactly what george zimmerman knew about florida's stand your ground law and when he knew it were the focus of today's murder trial. phil keating has the latest from sanford tonight. >> you see george over here? >> how you doing, george? >> reporter: george zimmerman's former criminal professor took the stand today after the judge ruled they can bring back his past passion for pursuing a career in law phone respectment due to zimmerman's own words played for the jury yesterday from a sean hannity interview a year ago. >> prior to this night, this incident, had you even heard of the stand your ground? >> no, sir. >> you'd never heard about it before? >> reporter: but zimmerman's former professor who gave zimmerman an a says he lectured stens differen extensively about the self-defense laugh. >> the students were very much engaged in class discussion regarding the issue. >> reporter: but on