SANFORD, Fla. -

Anthony Gorgone, a Florida Department of Law Enforcement analyst, identified three times as many stains on George Zimmerman's red jacket compared to Trayvon Martin's gray hoodie, he testified Wednesday.

Of the stains that tested positive for blood on Zimmerman's jacket, two were a partial match to Martin, Gorgone said. While Zimmerman's blood was found on the hem of Martin's undershirt, his DNA was not identified on the late teenager's hoodie.

Jurors also learned Martin's blood was discovered on his bag of skittles and investigators scraped the late teenager's fingernails for DNA.

Amy Siewert, another FDLE analyst, testified about the gun residue on Martin's clothing.

"The clothing displayed residues and physical effects consistent with a contact shot," she said.

The day began with jurors reviewing Zimmerman's homework and meeting his former professors.

"One of my best students," said Capt. Alexis Carter, Zimmerman's former college professor. "He was probably one of the better students in the class."

Carter testified Florida's "Stand Your Ground" law was discussed in classes Zimmerman took. In a July 2012 interview with talk show host Sean Hannity, Zimmerman said he didn't know the law.

Zimmerman has pleaded not guilty to second-degree murder, saying the shooting was in self-defense.

Special section: George Zimmerman trial