Nightly News | July 08, 2013
>>> at the trial in sanford, florida, george zimmerman 's defense team started its first full day presenting its case. on the stand, trayvon martin's father. the point of contention today? what he heard on the 911 call. our report tonight from nbc's ron mott.
>> reporter: today, defense attorney mark o'mara challenged trayvon martin's father about whether he told police the first time he heard the 911 call that it was not his son's voice screaming for help.
>> i kind of pushed away -- away from the table and shook my head and said i can't tell.
>> reporter: the prosecutor later listened to the tape at the mayor's office 20 times.
>> basically what i was listening to. i was listening to my son's last friday for he cry for help, listening to his life being taken, and i was coming -- trying to come to grips that trayvon was here no more.
>> reporter: earlier, the lead investigator offered a different reaction to the 911 tape.
>> i inquired if that was, in fact, his son yelling for help.
>> what was his response?
>> he -- he was more of a -- verbal and nonverbal. he looked away and under his breath and said. no.
>> reporter: one after another --
>> so you think he's yelling help?
>> reporter: five of zimmerman 's friends testified that its of his voice.
>> definitely georgie.
>> george .
>> george zimmerman 's voice.
>> no doubt that is george zimmerman .
>> reporter: this witness said that he donated thousands to zimmerman 's defense fund and worn the clothes that he has worn to court.
>> there is a bias on your behalf of george zimmerman , correct?
>> he is my very dear friend.
>> reporter: zimmerman said he shot martin in self defense after being attacked. late today, the judge ruled that the toxicology report can be admitted. showing martin had thc in his blood when he died, the active chemical in marijuana.
>> sgorgeorge zimmerman has sued nbc universal .