SANFORD, Fla. — After taking less than a week to call 18 witnesses, George Zimmerman’s defense attorneys rested their case Wednesday in the neighborhood watch volunteer’s second-degree murder trial.

Prosecutors and defense attorneys planned to work out the jury instructions before presenting closing arguments on Thursday. Judge Debra Nelson said the case could be sent to six jurors either late that day or the next.

Zimmerman never testified. But jurors saw repeated video recordings of Zimmerman telling his side of the story to investigators. He claims that he shot Trayvon Martin, who was unarmed, in self-defense while the teen straddled and punched him.

The defense started its case last Friday, and it presented half as many witnesses in half of the time that prosecutors did. Zimmerman’s friends, parents and uncle testified that it’s him screaming for help on a 911 call that captured sounds of the fatal fight. Martin’s mother and brother had testified for the prosecution that it’s Martin yelling for help.

Convincing the jury of who was screaming for help on the 911 tape became the primary goal of prosecutors and defense attorneys because it would help jurors evaluate Zimmerman’s self-defense claim.

Zimmerman’s father, Robert Zimmerman Sr., was the last witness called by the defense on Wednesday, and he said it’s his son yelling for help on the call.

Defense attorneys also called a forensic pathologist who testified that the forensics evidence supports Zimmerman’s account of what happened.

Zimmerman has pleaded not guilty to second-degree murder. On the night of the fatal scuffle in February 2012, Martin was visiting his father and his father’s fiancee at the same townhome complex where Zimmerman lived.

Zimmerman observed Martin while driving in his neighborhood, called police and the fight ensued after the neighborhood watch volunteer got out of his vehicle.

Some civil rights activists argued that the delay in charging Zimmerman was influenced by Martin’s race, and protests were held around the nation in the 44 days between the fatal fight and Zimmerman’s arrest. Martin was black and Zimmerman identifies himself as Hispanic.

The defense rested on a day when the judge made two rulings that prevented them from introducing pieces of evidence. Defense attorneys had wanted to present text messages discussing fighting from Trayvon Martin’s cell phone and an animation depicting Zimmerman’s fatal fight with Martin. But Nelson sided with prosecutors, who had argued the animation is inaccurate and the texts were irrelevant.

Immediately after the defense rested, prosecutors called their first rebuttal witness — Adam Pollock, the gym owner who had trained Zimmerman. But prosecutors decided not to question Pollock after the judge presiding over the case ruled he couldn’t be questioned about a video put on his gym’s website showing his court testimony at the trial.

Shortly after, court was adjourned until Thursday morning.