George Zimmerman's lawyer Mark O'Mara came in for a grilling from Al Sharpton on MSNBC in lengthy interview on last night.

Sharpton challenged O'Mara to explain how Zimmerman could he had acted in claim self-defense, when it was Zimmerman who pursued Trayvon Martin with a gun?

According to the Huffington Post, O'Mara countered that there was no evidence to support that Zimmerman continued to pursue Martin after calling 911, or that it was Zimmerman who initiated a physical confrontation.

But Sharpton replied that a panel of experts have said that the screams for help in the background of the 911 call belong Martin. O'Mara replied that other experts have said the voice is not easily identifiable.

Sharpton was unconvinced by O'Mara's argument, however. Later, when O'Mara stressed that the police need to have 'probable cause' before making an arrest, Sharpton replied:

'The probable cause is that you have the dead body of an unarmed person and there was no crime and there was no reason the police could determine at the scene. That's probable cause. Otherwise, anyone in this country could be shot and killed and the police could just decide in the police station, 'We'll decide whether they go or not.' That's a dangerous precedent, wouldn't you think so Attorney O'Mara?'

Zimmerman shot and killed Martin, an unarmed 17-year old, in February.

Martin's death and the local police's initial handling of the case prompted national outrage. Sharpton has himself been an advocate for Martin's family.

'We are tired of going to jail for nothing and others going home for something,' he said at a rally in March. 'Zimmerman should have been arrested that night,' Sharpton said.

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