Tracy Martin, the father of the late Trayvon Martin, testified in court on Monday in the second day of the defense’s case, as they attempt to prove George Zimmerman’s innocent of second-degree murder.

When the defense attorneys called Martin to the stand, they asked him to recall the conversation he had with Sanford police when first hearing the pivotal 911 call. He rejected previous testimony from Police Officer Christopher Serino that stated he had said he didn’t believe he heard his son’s voice. Martin admitted at first he said, “I can’t tell,” but after listening to the call over 20 times, he said, "I was listening to my son's last cry for help. I was listening to his life being taken."

The defense has called a number of family members and acquaintances of Zimmerman, who have testified that it was Zimmerman’s voice they heard on the 911 call. Zimmerman’s former co-worker Geri Russo stated, “I have no doubt in mind that’s his voice.” Meanwhile, both Trayvon Martin's surviving brother and mother have claimed the screams heard on the call are his.

On Monday afternoon, Circuit Judge Debra Nelson ruled that Trayvon Martin’s toxicology report, which shows he had trace amounts of marijuana in his system at the time of his death, would be permissible in court. Medical examiner Shiping Bao, who has wavered on his opinion of whether or not the amount of marijuana in the teen’s system affected him, will likely be recalled to the stand by the defense.

Also on Monday, Adam Pollock, the owner of a gym Zimmerman frequently trained in, served as a witness for the defense. While admitting the defendant had spent over a year taking boxing and grappling classes at his gym, stated his belief that he was “soft,” and a “beginner” who never developed significant strength, or learned how to punch.

Zimmerman, 29, is charged with the shooting death of Trayvon Martin, who was 17 on the night of the incident in February 2012. He is pleading not guilty by way of self-defense.

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