SANFORD, Fla. (AP) -- A prosecutor has gotten a judge to strike from the record an opinion from a Sanford police detective who testified that he found George Zimmerman credible in his account of how he got into a fight with Trayvon Martin.
Judge Debra Nelson on Tuesday told jurors to disregard the statement Detective Chris Serino made Monday.
Prosecutor Bernie de la Rionda said Serino's statement was improper because one witness isn't allowed to give an opinion on the credibility of another witness.
Defense attorney Mark O'Mara says the opinion is proper because Serino was vetting Zimmerman's veracity during his probe.
Zimmerman is pleading not guilty to second-degree murder, claiming self-defense.
The lead police detective who investigated the fatal shooting of Trayvon Martin in central Florida last year was to return to the witness stand Tuesday for a second day to testify about his investigation.
Sanford Police detective Chris Serino and another investigator, Doris Singleton, testified Monday about their investigation as jurors heard a series of police interviews in which the detectives grow more pointed in their questioning of George Zimmerman, the neighborhood watch volunteer later charged with second-degree murder in Martin's death. Zimmerman maintains he was acting in self-defense.
In an early interview, just hours after the Feb. 26, 2012, shooting, Singleton recounted that Zimmerman noticed a cross she was wearing and said: "In Catholic religion, it's always wrong to kill someone."
Singleton said she responded, "If what you're telling me is true, I don't think that what God meant was that you couldn't save your own life."
But in an interview days later, Singleton and Serino suggest that Zimmerman was running after Martin before the confrontation. They also ask Zimmerman why he didn't explain to Martin why he was following him. The officers insinuate that Martin may have been "creeped out" by being followed.
"Do you think he was scared?" Singleton asked Zimmerman in one video interview.
Under cross-examination, though, Serino said Zimmerman seemed straightforward in his answers and didn't show any anger when talking about Martin. Serino said the increasingly pointed questioning is a tactic known as a "challenge interview," where detectives try to break someone's story to make sure they're telling the truth.
Zimmerman has said he fatally shot the unarmed black teen in self-defense in February, 2012, because he says Martin was banging his head into a concrete sidewalk behind townhomes in a gated community in Sanford, Fla. Zimmerman, 29, could get life in prison if convicted of second-degree murder.
The state argued during its opening statement that Zimmerman profiled and followed Martin in his truck and called a police dispatch number before he and the teenager got into a fight. Zimmerman has denied the confrontation had anything to do with race, as Martin's family and their supporters have claimed. A 44-day delay in Zimmerman's arrest led to protests around the nation; he was ultimately charged by a Florida special prosecutor. Zimmerman's father is white and his mother is Hispanic.
In his first interview at the police station, Zimmerman said he saw Martin walking through his neighborhood on a dark, rainy night while Zimmerman was driving to the grocery store. He told Singleton that he didn't recognize Martin and that there had been recent break-ins at his townhome complex.
"These guys always get away," Zimmerman told Singleton, a statement similar to one that prosecutors have pointed to previously to try to show that Zimmerman was increasingly frustrated with the burglaries and that his encounter with Martin was a breaking point.
Zimmerman told the police officer that he lost track of Martin and got out of his truck to look for a street name he could relay to a police dispatcher. When the dispatcher suggested Zimmerman didn't need to follow Martin, Zimmerman started to head back to his vehicle. At that point, Zimmerman alleged, Martin jumped out of some bushes, punched him and he fell to the ground.
Zimmerman said Martin began hitting his head against the sidewalk as Zimmerman yelled for help and that Martin told him, "You're going to die tonight."
With Zimmerman's shirt and jacket pushed up during the struggle and his holstered gun now visible, he thought Martin was reaching for his firearm holstered around his waist. Zimmerman told the officer that he shot Martin and the teen said, "You got me."
In a written statement, Singleton read in court, Zimmerman refers to Martin as "the suspect." Singleton said it didn't appear that Zimmerman showed any anger when talking about the teen. Prosecutors must show that Zimmerman acted with ill will or a depraved mind in order to get a second-degree murder conviction.
Zimmerman also acted surprised when Singleton told him Martin was dead.
"He's dead?!" Singleton recalled Zimmerman saying, before he lowered his head toward the table in the interrogation room.
Earlier Monday, prosecutors called FBI audio expert Hirotaka Nakasone to focus on the issue of who was screaming for help on 911 calls during the confrontation. Jurors were played the 911 calls several times last week.
The recordings are crucial pieces of evidence because they could determine who the aggressor was in the confrontation. Martin's family contends it was the teen screaming, while Zimmerman's father has said it was his son.
Even though he was a pre-trial witness for the defense, prosecutors called Nakasone to set up later testimony from either the teen's mother or father that they believe it was their son yelling for help.
During his pre-trial testimony, Nakasone testified that there wasn't enough clear sound to determine whether Zimmerman or Martin was screaming on the best 911 sample, an assertion he repeated Monday.
The FBI expert said it's easier for a person with a familiarity of a voice to identify it than someone who has never heard it previously. That is especially true if the recording is of a subject screaming and the person trying to identify the voice has heard the subject under similarly stressful circumstances previously, Nakasone said.