Expert witness: Zimmerman’s head wounds not life-threatening

>>> in florida today , at the george zimmerman trial, prosecutors tried to chip away at his claim that he feared for his life the night he shot and killed trayvon martin. nbc's ron mott reports from the courthouse in sanford, florida.

>> reporter: today a medical examiner analyzed george zimmerman 's injuries.

>> could all the injuries that you ovg eobserved in that photograph have come from a single punch or a single blow?

>> yes about.

>> reporter: his head wounds were not life threatening and not in line with his account of being slammed into a sidewalk over and over .

>> are the injuries to the back of the defendant's head consistent with having been repeatedly slammed into a concrete surface?

>> no.

>> why not?

>> if you look at the injuries, they're sao minor, that to me, the word slam implies great force. and this -- the resulting injuries are not great force.

>> but the defense got her to admit zimmerman 's injuries could have been caused by multiple impacts.

>> anything that would medically exclude that the right side was hit four times?

>> it's possible.

>> zimmerman , who has pleaded not guilty to second degree murder said he shot trayvon martin in self-defense while being attacked. earlier, lead investigator chris sorino returned to the stand for a second day of testimony.

>> any inconsistencies that you consider to be significant?

>> none which i can challenge him with, so i would say no.

>> reporter: the prosecutor asked about zimmerman 's use of profanity in his call to police. reporting a suspicious person in your neighborhood?

>> in your opinion, calling someone to reference them as [ bleep ] punks --

>> that is ill will and spite.

>> reporter: ill will , spite, hatred or evil intent are all factors the state must prove. the prosecutor worked to prove he was following martin that night.

>> you said following him is not legally improper, correct?

>> it's not illegal.

>> tomorrow the judge may decide if zimmerman 's college records as a criminal justice major can be admitted. ron mott, nbc news, sanford, florida.