SANFORD -- Defense attorneys presented a parade of witnesses Monday who testified, one by one, that the chilling screams on a 911 call came from their friend, George Zimmerman.

And jurors soon will learn that Trayvon Martin had marijuana in his system on Feb. 26. 2012, the night Zimmerman shot him. Seminole County Circuit Judge Debra Nelson, who had previously held off on a ruling on the toxicology report’s admissibility, said late Monday she would let the defense present the information to jurors in Zimmerman’s second-degree murder trial, now entering its third week of testimony. Prosecutors rested the state’s case on Friday.

Defense attorneys seemed to gain momentum Monday with testimony from two Sanford police investigators who said that Tracy Martin, the father of slain 17-year-old Trayvon, told them the screams on the recorded call did not belong to his son.

But, in what legal observers said was a risky move, defense lawyers then called Tracy Martin to the stand. He remembered a different version of what he told police after they played him the 911 call two days after Zimmerman fatally shot Trayvon in a gated Sanford community.

Investigator Chris Serino “basically just said, ‘Do you recognize the voice?’” Martin said. “My response was... I pushed my chair away from the table, shook my head and said I can’t tell. I never said, ‘No, that wasn’t my son’s voice.’”

Later, Martin said, he recognized the voice as his son’s.

“After listening to the tape maybe 20 times, I knew that it was Trayvon’s voice.”

Monday’s list of defense witnesses — the first five, including two married couples, said they believed they heard Zimmerman yelling for help on the 911 call — served to counter testimony Friday from Trayvon’s mother and brother, both of whom identified the voice crying out for help as belonging to the slain Miami Gardens teen.

The defense witnesses also offered testimony aimed at bolstering the image of the defendant, a former neighborhood watch coordinator who prosecutors are painting as a frustrated, wannabe cop. Zimmerman, 29, maintains he acted in self-defense after Trayvon violently attacked him. Zimmerman faces up to life in prison if convicted as charged.

One couple, John Donnelly and Leanne Benjamin, spoke of Zimmerman in parent-like fashion. She talked about mentoring the defendant in starting his own business, while her husband choked up a bit when he described buying Zimmerman suits for the trial and teaching him to tie a Windsor knot.

Another Zimmerman pal, Mark Osterman, previously called as a state’s witness, took the stand Monday as a defense witness, telling jurors about teaching his “best” friend about firearm safety. Osterman’s wife, Sondra, who also took the stand, repeatedly referred to Zimmerman as “Georgie” and identified the voice on the 911 call as Zimmerman’s.

“The voice witnesses on both sides will probably cancel each other out, especially because each one has a built-in bias,” said former Miami-Dade prosecutor David Waksman, who watched part of Monday’s testimony.

“But for the defense, these witnesses were important to humanize the defendant. They want him to be Georgie, George, your next-door neighbor.”