SANFORD, Fla. -- The defense in the George Zimmerman case Wednesday completed presenting its case to the jury, which will soon begin deliberations on whether the neighborhood watch volunteer murdered Trayvon Martin or shot the unarmed teenager in self-defense.

Zimmerman, 29, chose Wednesday not to take the stand in the proceedings, which began with jury selection a month ago. Zimmerman has given several versions of the events of the night of Feb. 26, 2012, when he and Martin had their confrontation in Sanford, and would have been a ripe target for a vigorous cross-examination.

Closing arguments in the case, which galvanized civil rights leaders across the nation, could come as soon as Thursday. Judge Debra S. Nelson will then instruct the six-woman jury before it begins deliberating.

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The defense took less than four full days to present its case, which included fewer than 20 witnesses, some of whom also testified for the prosecution. The prosecution, which has the burden of proving that Zimmerman committed second-degree murder as charged, called about three dozen witnesses and took nine days to present its case.

After Nelson earlier Wednesday ruled against two defense motions requesting that an animated reconstruction be admitted into evidence along with texts from a cellphone, most of the rest of Wednesday was taken up by the testimony of Dennis Root, a safety consultant.

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Root testified that Martin was in better physical shape than Zimmerman, and that the neighborhood watch volunteer wasn't any athlete. The testimony echoed a similar assessment Tuesday by the gym owner where Zimmerman trained.

Zimmerman “would find himself lacking when compared to Mr. Martin,” Root said.

During cross-examination, the prosecution brought out its own audio-visual aid, a life-sized, pliable foam dummy that was used to simulate different sets of positions between Zimmerman and Martin.  Straddling the dummy, prosecutor John Guy asked Root if it was possible that Martin was backing away from Zimmerman at the time of the fatal gunshot.

“Yes,” Root said, supporting the prosecution’s position.

Defense attorney Mark O’Mara challenged the theory that Martin was retreating. Root eventually said that while multiple gun angles were possible, he had no specific information to say what position Martin was in.

In its case, the defense also called its own forensic expert, who testified that the medical evidence was consistent with Zimmerman’s account of events the night Martin was killed.

Martin, 17, was returning from a convenience store where he bought candy and a soft drink. He was going to the home of a friend when he was spotted by Zimmerman and the confrontation occurred.

Zimmerman maintains he shot Martin in self-defense.

Susman reported from Sanford and Muskal from Los Angeles.

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