Trayvon Martin's testimony wouldn't have changed anything in Zimmerman trial

In the days since 17-year-old Trayvon Martin was shot and killed by 28-year-old George Zimmerman, a common claim has been: "we will never know what happened between Zimmerman and Martin since the only person who knows the truth and is still alive is Zimmerman."

But this statement is not accurate. The closing arguments in Zimmerman's case start today. And the truth is, we know a lot about what happened on that fateful night. Trayvon Martin's testimony, could he have spoken, wouldn't changed anything.

For those who have watched the trial, ask yourself: is there even one piece of convincing evidence that Zimmerman did not act to defend himself from a threat of “imminent death or great bodily harm”?

There is a reason that the local District Attorney refused to bring the case against Zimmerman and an outside District Attorney had to be brought in to handle it. And that the chief of police was also removed from his job because he refused to charge Zimmerman with a crime. Also consider that the lead detective on the case told the jury he believed Zimmerman's version of the events that happened.

If both Zimmerman and Martin had both been white or if Zimmerman had been darker skinned, this case would never have gotten to court.

There was no convincing evidence to support the charges against Zimmerman.

The problem the prosecution faced should have been glaring to anyone familiar with criminal trials.

When I was chief economist at the U.S. Sentencing Commission I read hundreds of trial transcripts. Prosecutors consistently put police and their experts on the witness stand early in the trial because they used them to sketch out the theory of the case. Things were different in the Zimmerman trial. Here, prosecutors began with weak testimony from witnesses -- people who either really couldn't tell what they had seen or who couldn't be sure what had happened.

The debate among the forensic experts wasn't over who suffered injuries. Everyone agreed that there were wounds on Martin's hands and none on Zimmerman's hands.

Both the front and back of Zimmerman's head suffered wounds, while no similar wounds were found on Martin. The prosecution experts provided no evidence contradicting Zimmerman's claim that Martin was on top of him when he was shot.

Zimmerman's expert, Dr. Vincent Di Maio -- the man whose book the Sanford medical examiner had referenced to as the authority on the subject -- explained from both the angle of the bullet’s entry into the body and its distance from the Martin's body that Martin was on top of Zimmerman.

The debate between the experts was over how severe Zimmerman's wounds were.

After examining photos of Zimmerman immediately after the attack, Jacksonville medical examiner, Valerie Rao, claimed that they were "insignificant," that there was "a chance" that the number of blows Zimmerman suffered could range from just one to more than a half dozen. She wouldn't say what the maximum number could be.

Di Maio pointed out that you can't judge the severity of blows from photos and certainly not just the photos taken right at the time of the injury as patterns of injury can only be revealed based on how bruising changes over time. Furthermore she said that "You can have severe head trauma without any marks on the head." Di Maio identified six separate blows that were landed on Zimmerman's face and head.

Witnesses saw the struggle between Zimmerman and Trayvon Martin.

One witness who had by far the clearest view, Jonathan Good, was only 15 to 20 feet away immediately before the shot was fired. His testimony on the color of the men's clothes and skin confirmed that Martin was on top of Zimmerman, straddling and pummeling him.

If Martin had been alive today, what could his testimony have added to any of this?

Could he have explained away the angle of the bullet?

What would Martin have said about why his knuckles and Zimmerman's head showed signs of bruising?

With Zimmerman's broken nose and lacerations on the back of his head, would it have mattered if Martin had told the court that he really hadn't hit Zimmerman that hard?

The prosecution never provided any evidence that Zimmerman continued following Martin after the 911 operator suggested that he stop doing so.

Suppose Martin could testify that Zimmerman had continued to follow him, would that have mattered?

No, because even if Martin had indeed been followed, it wouldn’t have justified Martin punching Zimmerman’s nose, pinning him down and repeatedly hitting him and slamming his head into the concrete.

Suppose Martin had claimed -- along with his mother, father and brother -- that he was the one screaming for help. Would that have really mattered?

Would that have offset the all the witnesses who said that Zimmerman was the one screaming? Under cross examination, how would Martin have explained that he was one calling for help when he was the one on top of Zimmerman and hitting him?

Tuesday’s testimony from the city manager highlighted how political considerations interfered with the investigation. When police had presented that evidence to Martin's father they learned that his father didn't recognize the screams as coming from his son.

But then Sanford City Manager Norton Bonaparte intervened in the police investigation and kept the police out of the room when the 911 call with the screams was played for Martin's mother.

The political and racial angle of this case -- that has been inflamed by President Obama, Al Sharpton and many others -- has left lasting damage to race relations in the U.S.

As Zimmerman’s defense attorney Mark O'Mara remarked this week: "my client will never be safe because there are a percentage of the population who are angry, they're upset and they may well take it out on him. So he'll never be safe."

Zimmerman’s right to defend himself has already saved his life once. Unfortunately, with the anger generated by those seeking political gain from the case, he might unfortunately need to defend himself yet again.

John R. Lott Jr. is a FOXNews.com contributor. An economist and former chief economist at the United States Sentencing Commission, he is also a leading expert on guns. He is the author of several books, including "More Guns, Less Crime." His latest book is "At the Brink: Will Obama Push Us Over the Edge? (Regnery Publishing 2013).". Follow him on Twitter@johnrlottjr.