Former neighborhood watch volunteer George Zimmerman was well versed in Florida's self-defense laws before he shot and killed unarmed black teenager Trayvon Martin, despite a previous claim to the contrary, jurors were told at Zimmerman's trial on Wednesday.

The contradiction came into evidence as prosecutors were preparing to wrap up their case on Friday after two weeks of testimony aimed at showing inconsistencies in Zimmerman's accounts of the February 2012 shooting.

On Tuesday, Seminole County Judge Debra Nelson let the jury hear a television interview in which Zimmerman said he had no knowledge of Florida's "Stand Your Ground" law, which underpins his trial defense.

But an army prosecutor who taught Zimmerman in a 2010 college class on criminal litigation, testified that he often covered Florida's self-defense and "Stand Your Ground" laws in his 2010 course. Army Captain Alexis Carter said Zimmerman "was probably one of the better students in the class," calling him an "A" student.

Under the "Stand Your Ground" law, which was approved in 2005 and has been copied in some form by about 30 other states, people fearing for their lives can use deadly force without having to retreat from a confrontation, even when it is possible.

The statute is central to Zimmerman's defense in a case that captivated the United States throughout much of 2012 because police initially declined to arrest Zimmerman based on his self-defense argument and right to use deadly force under Florida law.

Zimmerman has pleaded not guilty to a charge of second-degree murder, saying he shot Martin in self-defense during their confrontation inside a gated community in the central Florida town of Sanford on Feb. 26, 2012.

In allowing evidence about Zimmerman's criminal law studies, the judge overruled strenuous objections from Zimmerman's lead lawyer, Mark O'Mara.

Prosecutor Richard Mantei had said during a hearing that Zimmerman's legal studies would help jurors understand his "state of mind" and "ambitions and frustrations" in the weeks and months leading up to the shooting.

Prosecutors say Zimmerman's choice of classes at Seminole State College, on criminal investigation and witness testimony among other topics, underscored his intense interest in law enforcement and previous interest in becoming a police officer.

DNA EXPERT

In testimony on Tuesday, the jury heard a medical examiner say Zimmerman suffered "insignificant" injuries in the fight in which he shot and killed Martin.

Zimmerman, 29, has said Martin, 17, punched him in the face and repeatedly slammed his head into a concrete walkway. Zimmerman, who is white and Hispanic, could face life in prison if convicted.

Despite those claims, a DNA expert with the Florida Department of Law Enforcement testified on Wednesday that none of Zimmerman's DNA was found in scrapings of Martin's fingernails or on the cuffs or other parts of the hooded sweatshirt he wore on the night he died.

There was also no trace of Martin's DNA on Zimmerman's gun, the expert, Anthony Gorgone, told the court. Zimmerman has said Martin tried to grab the 9mm Kel-Tec semi-automatic before he shot him at point-blank range.

Police initially declined to arrest Zimmerman, accepting his story of self-defense.

A special prosecutor later brought the murder charge. The prosecutor accused Zimmerman of profiling Martin and chasing him vigilante-style rather than waiting for police to arrive.

Martin was a student at a Miami-area high school and a guest of one of the housing development's homeowners. He was walking back to the home in the rain from a convenience store when Zimmerman spotted him and called police, saying Martin looked suspicious. During the confrontation between the two, which is still clouded by competing narratives and conflicting witness testimony, Zimmerman shot Martin through the heart.

Assistant State Attorney Bernie de la Rionda had said he hoped to rest the prosecution's case against Zimmerman on Wednesday but court adjourned before he was able to call his final witnesses.

The court will be closed on Thursday for the U.S. Independence Day holiday so the final state witnesses, including the medical examiner who autopsied Martin's body and the dead teenager's parents, won't take the stand until Friday.