The questions, and answers, are important because they speak to Mr. Zimmerman’s credibility in a case that rests squarely on his account of what happened that night. The Sanford Police Department was widely criticized after the shooting for failing to fully investigate the case, especially on the first night. Law enforcement did not immediately bring charges in the case, setting off a national outcry about race and Florida’s self-defense laws. On Wednesday, Bill R. Lee Jr., Sanford’s police chief, was fired.

But, by and large, Mr. Zimmerman stuck to his account during the questioning. Mr. Martin circled his car while he was on the phone to police dispatch. Mr. Martin reached for his waistband and then walked away. At that point, Mr. Zimmerman got out of the car and walked in the same direction to see the name of the street to phone it in.

On his way back to the car, Mr. Martin appeared out of nowhere and asked him, “Do you have a problem?” The answer was no. “You do now,” Mr. Zimmerman said Mr. Martin told him. Mr. Martin then attacked Mr. Zimmerman as he tried to use his cellphone to dial 911.

Mr. Zimmerman was firm in his central self-defense claim: He did not show his gun before the fight and he did not provoke Mr. Martin.

During the questioning on Feb. 26, 27 and 29, Mr. Serino did not seem aggressive or hostile. Calling Mr. Zimmerman a “good guy,” he repeatedly gave him a chance to explain portions of his statement that troubled the police. Mr. Serino is heard in one of the recordings repeatedly warning Mr. Zimmerman that public opinion, already tilting against the crime watch volunteer, would pillory him unless he could explain exactly why he felt justified in pulling the trigger at an unarmed “kid with a future.”

Mr. Martin was no “goon,” Mr. Serino told Mr. Zimmerman. He was an athlete. His parents cared about him. He had no violent history, and he was armed with only a pack of candy and a can of iced tea.

“Everybody wants to know what sets him off,” Mr. Serino said. “He’s not on PCP. He’s not on anything. He’s on Skittles.”