(CNN) -- On Monday, for the first time, jurors in the George Zimmerman trial heard from the former neighborhood watch volunteer about the events that led to Trayvon Martin's death on Feb. 26, 2012.

"I tried to defend myself," Zimmerman said during his first police interview the night of the shooting. "He just started punching me in the face, and I started screaming for help. I couldn't see. I couldn't breathe."

As the trial began its second week, prosecutor Bernie De La Rionda played the audio recording of the police interview conducted at the Sanford, Florida, Police Department headquarters.

Tape of Zimmerman's retelling of the confrontation between himself and Martin could bolster the defense's key contention: that Zimmerman reacted in self-defense.

Zimmerman began his interview with investigator Doris Singleton by saying that there had been a lot of crime in the area and that he had started a neighborhood watch program. He said he spotted Martin, who he thought looked suspicious, and began to follow him.

At some point, Martin circled Zimmerman's car as he followed him through the neighborhood, Zimmerman said, and then the teenager disappeared into the "darkness."

Zimmerman said he told the 911 dispatcher he got out of his car to find out where Martin went.

"The dispatcher told me 'Where are you?' and I said 'I am trying to find out where he went,' and he said, 'We don't need you to do that,' and I said 'OK,'" Zimmerman told the investigator.

Zimmerman then started to head back to his car, he said, but never got there.

"He (Martin) jumped out from the bushes, and he said 'What the (expletive) is your problem, homie?' and I got my cell phone out to call 911 this time, and I said, 'I don't have a problem.' And he goes, 'Now you have a problem,' and he punched me in the nose," Zimmerman said.

Zimmerman said the blow knocked him to the ground, Martin got on top of him, and Zimmerman yelled for help.

"He puts his hand on my nose and my mouth, and he says, 'You are going to die tonight," Zimmerman said. "As he banged my head again, I just pulled out my firearm and shot him."

He added, "He is mounted on top of me, and I just shot him, and he falls off. And he's, like, 'Alright you got it, you got it.'"

Earlier Monday, in a surprise move, prosecutors called FBI senior scientist Hirotaka Nakasone to the stand to testify on whether it was possible to conduct voice analysis of the screams on the 911 call from the night of the shooting.

Nakasone has already testified as a defense witness in an evidentiary hearing about the admissibility of voice analysis technology, and was slated to be called by the defense during its case.

Nakasone said the science of voice recognition cannot reliably identify the screams on the call, and someone who knows the person was screaming on the call may be the best person to identify the voice. Prosecutors may have called Nakasone to help support the testimony of Martin's parents, who may testify that they recognize the screams as coming from their son.

Referring to the limitations of the technology, defense attorney Don West asked, "Science really doesn't help us in this case figure out who is screaming?"

"Unfortunately, that is correct," Nakasone said.

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