holy [bleep]. >> reporter: john good made that 911 call the night george zimmerman shot and killed 17-year-old trayvon martin. on day five of the second degree murder trial, prosecutors used good's testimony and original stick figure sketch for police to challenge zimmerman's claim that martin repeatedly pounded his skull into the sidewalk and suggested his use of deadly force was not justified. >> did you ever see the person on top slamming the person on the bottom's head on the concrete over and over and over? >> no. >> did you see at any time the person on top grab the person on the bottom's head, slam it into the concrete. >> no. >> reporter: on cross examination, zimmerman's attorney scored getting him to identify martin as the one on top and identify the person yelling for help. >> you now believe that was george zimmerman's voice. tell us if you think that was george zimmerman's voice screaming for help, the person on the bottom. >> that's just my opinion.