Tracy Martin, the father of the teenager shot by George Zimmerman, took the stand Monday to rebut claims about who is heard screaming on a 911 recording that could be pivotal in the jury's deliberations in the high-profile murder trial.
In the first full day of the defense's case, the sides sparred over whose voice is heard in the background of a call placed to authorities.
The issue of who is crying out for help could be important as the jury tries to decide who the aggressor was: Zimmerman, the neighborhood watch volunteer, or Trayvon Martin, the teenager.
Martin's father denied that he told a police investigator that the screams were not his son's.
"I didn't tell him it wasn't Trayvon," Tracy Martin testified. He said he replied, "I can't tell," when police played the recording and questioned him days after the fatal confrontation.
Zimmerman, 29, is charged with second-degree murder in the shooting of Martin, 17, on Feb. 26, 2012, during an altercation in a gated community in Sanford, Fla. Zimmerman says he shot Martin in self-defense.
Under cross-examination, Tracy Martin recalled meeting with police and listening to the recording.
"I listened to my son's last cry for help, listened to his life being taken," he said of the first time he heard the tape. "I was trying to come to grips."
Last week, Trayvon Martin's mother and brother testified that the screams heard on the recording were Martin's. Zimmerman's mother and uncle testified last week that the screams belonged to Zimmerman. On Monday, several friends of Zimmerman testified that they recognized the voice as his.
Earlier, two police investigators testified that Tracy Martin told them that the screams on the recording were not the voice of his son.
Investigator Christopher F. Serino, who was called earlier in the trial as a prosecution witness, described the meeting. Serino said he asked Tracy Martin whether the voice on the recording was his son's. The answer was no, Serino said.
"It was more of a verbal and nonverbal answer," Serino said. "He looked away and said something under his breath. As I interpreted it, he said no."
When pressed on cross-examination about whether he was sure, Serino said, "I heard it and saw the movement of his mouth."
Prosecutor Bernie de la Rionda suggested during cross-examination that Tracy Martin may have said "no" out of denial about his son's death.
"It could be perceived as denial," said Serino, agreeing that listening to the recording was emotional for Tracy Martin.
Officer Doris Singleton, who also testified earlier in the trial and was present at the interview with Tracy Martin, said he had appeared very upset.
Singleton testified that she had no doubt that Tracy Martin had indicated that it was not his son's voice on the recording. The officer gave a slightly different version of events than Serino, but corroborated the main point that Tracy Martin told Serino "that it was not his son," Singleton testified.
The defense called witnesses who were familiar with Zimmerman's voice. They identified the neighborhood watch volunteer as the person screaming on the recording.
"Definitely it's Georgie," the day's first witness, Sondra Osterman, said after defense attorney Mark O'Mara played the recording of the now-famous call, in which several loud cries and a single gunshot can be heard.
After Tracy Martin testified, jurors were sent away for the day so the attorneys could argue several motions.
Judge Debra S. Nelson ruled that the toxicology report on Martin would be allowed. The report shows that Martin had a small amount of marijuana in his system the night he was shot.