No DNA from Trayvon Martin on Zimmerman's gun

(CNN) -- Prosecutors in the George Zimmerman trial presented evidence of DNA test results to the jury Wednesday that showed where Zimmerman's and Trayvon Martin's genetic material ended up during their 2012 altercation.

Anthony Gorgone, DNA lab analyst for the Florida Department of Law Enforcement, methodically walked the jury through the results of his DNA testing of Zimmerman's gun, the clothing both individuals wore the night of the shooting and scrapings from Martin's finger nails.

Zimmerman did not show any emotion as Gorgone testified, but he appeared to be paying close attention.

Zimmerman is charged with second-degree murder for killing 17-year-old Martin in Sanford, Florida, on February 26, 2012. Zimmerman told police that the teenager looked suspicious and that there had been several break-ins in the neighborhood. The two got into a physical altercation, and Zimmerman said he was forced to draw his gun and kill Martin in self-defense.

Protests were held around the country when it appeared Zimmerman wasn't going to be arrested in Martin's death. Zimmerman was eventually charged with second-degree murder in April 2012. The case has reinvigorated national conversations about race, racial profiling and self-defense laws.

Gorgone testified Wednesday that he found only Zimmerman's DNA on the gun he used to shoot Martin and did not find any of Martin's DNA on the gun. Zimmerman's holster tested positive for only Zimmerman's DNA as well. Zimmerman has said that Martin grabbed his gun during the altercation.

Gorgone testified that testing of Martin's hooded jacket that he was wearing as an outer layer the night of shooting did not yield much of Zimmerman's DNA. Only one stain on Martin's hooded jacket yielded a partial DNA profile that matched Zimmerman. Scrapings from under Martin's fingernails yielded none of Zimmerman's DNA.

Martin was also wearing a gray sweatshirt under his hooded jacket. Gorgone said two stains on that sweatshirt matched both Martin's and Zimmerman's DNA.

During cross examination, defense attorney Don West pointed out that Martin's sweatshirts were wet from rain the night of the shooting, and they were not allowed dry before they were stored in plastic bags. Gorgone said if wet evidence is not left to air dry before being stored in plastic, mildew can degrade DNA evidence.

West asked, "Frankly then you just didn't find much of anything on this gray hooded sweatshirt when it boils right down to it?"

"Just that partial profile on stain A" said Gorgone.

West asked, "That was the shirt that stunk to high heaven?"

"It didn't smell good," said Gorgone.

Earlier Wednesday, prosecutors called several witnesses to help support their assertion that the former neighborhood watch captain was a "wannabe cop" who knew Florida's self-defense and "Stand Your Ground" laws well.

Records admitted into evidence on the eighth day of testimony included a letter rejecting Zimmerman's application to be a police officer in Virginia in 2009 because of his credit issues. A release form filed with the Sanford Police Department lists Zimmerman's reason for wanting to ride along with them as to "solidify my chances of a career in law enforcement." Records also indicate Zimmerman applied for a diploma in criminal justice in 2011 at Seminole State College in Florida.

The instructor who taught Zimmerman's criminal litigation class testified Wednesday that he covered Florida's self-defense laws extensively, even though there was no mention of them in the course book. "It's not one of those things that you're just going to whisk through in a day," said Alexis Carter, who is now a military prosecutor.

The testimony seemed to counter a key claim that Zimmerman made last year in a Fox News interview that was replayed in court: that he didn't know about Florida's "Stand Your Ground" laws until after the shooting.

Self-defense laws were "something that I constantly iterated ... it was something that I think the students really wanted to know about, it was so practical, they were very much engaged in class discussion," Carter said. He called Zimmerman "one of the better students" in his class and said he gave him an A. He also said he taught his students about "imperfect self-defense," which he said means "the force that you are encountering, you meet that force disproportionately -- excess force. Like a gunshot."

Prosecutors say that while evidence showing that Zimmerman wanted to be a cop isn't "bad," they hope it will give jurors some insight into his thought process the night he shot and killed Martin. They also suggest that his studies in criminal justice show Zimmerman knew how to testify and talk to police.

Scott Pleasants, another Seminole State College teacher, testified Wednesday via webcam about the criminal investigations class in which Zimmerman was a student. He says that while the course book covered profiling and how to testify as a witness, they never actually discussed it in class.

A bizarre moment occurred when several Skype users started flooding prosecutor Richard Mantei's account with calls. "There's a really good chance we're being toyed with," defense attorney Mark O'Mara said. Pleasants was able to resume his testimony via speakerphone, and the proceedings continued.

A firearms expert with the Florida Department of Law Enforcement, Amy Siewert, examined Zimmerman's gun and said he had one bullet ready to fire in the chamber as well as a fully loaded magazine when he fatally shot Martin.

"They're not much use if they're not ready to fire, are they?" asked O'Mara.

"No," said Siewert.

The defense got her to agree that many law enforcement agents carry fully loaded weapons that are ready to fire. Siewert also showed jurors how the gun wouldn't fire accidentally; the trigger has to be pulled. But Siewert wouldn't go so far as to call the loaded gun "safe," saying it's a matter of personal preference.