A friend who was on the phone with 17-year-old Trayvon Martin moments before he was fatally shot by George Zimmerman testified that she heard the U.S. teen shout, "Get off! Get off!" before his telephone went dead.

Rachel Jeantel, 19, recounted to jurors in Zimmerman's murder trial how Martin told her he was being followed by a man as he walked through a gated Florida community on his way back from a convenience store to the home of his father's fiancee.

The case has drawn attention to race _ Martin was black _ and self-defense laws.

Jeantel is considered one of the prosecution's most important witnesses because she was the last person to talk to Martin before his encounter with Zimmerman on Feb. 26, 2012.

She testified that Martin described the man following him as "a creepy-ass cracker" and he thought he had evaded the man. But she said a short time later Martin cursed.

Martin said Zimmerman was behind him, and she heard Martin ask: "What are you following me for?"

She then heard what sounded like Martin's phone earpiece drop to the ground, and she heard him say, "Get off! Get off!" The phone went dead, she said.

Zimmerman, 29, could get life in prison if convicted of second-degree murder.

Zimmerman has claimed self-defense, saying he opened fire after the teen jumped him and began slamming his head against the concrete sidewalk. Zimmerman identifies himself as Hispanic and has denied that his confrontation with the black teenager had anything to do with race, as Martin's family and its supporters have claimed.

Martin's parents have said they believe that cries for help heard by neighbors came from their son, while Zimmerman's father believes the cries belong to his son. Both prosecutors and defense attorneys believe they could show whether Zimmerman or Martin was the aggressor in the encounter.

Before the shooting, Zimmerman had made about a half dozen calls to a nonemergency police number to report suspicious characters in his neighborhood. Prosecutors have argued that the calls show his state of mind. He was increasingly frustrated with repeated burglaries and had reached a breaking point, prosecutors say.

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Associated Press writers Mike Schneider and Kyle Hightower contributed.