SANFORD -- Medical evidence supports George Zimmerman’s claims that he was beaten and on the bottom of a scrum with Trayvon Martin when Zimmerman fatally shot the Miami Gardens teen, a forensic-pathology expert testified Tuesday.

“This is consistent with Mr. Zimmerman’s account that Mr. Martin was over him, leaning forward at the time he was shot,” defense witness Dr. Vincent Di Maio said in Zimmerman’s second-degree murder trial.

Prosecutors accuse Zimmerman, 29, of profiling, pursuing and slaying Trayvon, 17, in a Sanford gated community on Feb 26, 2012. Zimmerman, a former neighborhood-watch coordinator, maintains that he shot the unarmed teen in self-defense after Trayvon punched him to the ground and bashed his head against a sidewalk. A 44-day gap between Trayvon’s killing and Zimmerman’s arrest led to marches and protests throughout Florida and elsewhere in the country.

On Tuesday, Di Maio, a former longtime San Antonio chief medical examiner and author of a textbook called Gunshot Wounds, turned his head toward jurors as he answered lawyers’ questions in a commanding voice.

The doctor’s findings, based on a review of Trayvon’s autopsy report, photographs and other evidence in the case, contradicted several witnesses who testified for the state, which rested its case last week. He also pointed out what he said were forensic flaws in the initial investigation.

Di Maio said he concluded:

•  DNA and other evidence from Trayvon’s hooded sweatshirt may have been compromised because crime-scene technicians improperly stored Trayvon’s wet clothes in plastic bags. Wet evidence should be allowed to dry out and be packaged in paper bags that allow it to “breathe,” Di Maio said.

•  Gunpowder markings on Trayvon’s body and sweatshirt indicated that the muzzle of Zimmerman’s gun was touching the sweatshirt and was two to four inches from Trayvon’s chest when Zimmerman pulled the trigger.

Dr. Shiping Bao, the associate medical examiner who conducted Trayvon’s autopsy, testified for the state last week that the gun could have been anywhere from a half-inch to four feet from Trayvon; prosecutor John Guy said in his opening argument that Zimmerman had pressed his gun into Trayvon’s chest.

“This is basic, you know, 101,” Di Maio said of the gunshot evidence.

•  Trayvon would have been able to talk and move for a minimum of 10 to 15 seconds after being shot. Zimmerman told investigators that Trayvon said something like “you got it” or “you got me” immediately after he was shot.

“If I reached over and ripped out your heart, you could stand there and talk to me for 10 to 15 seconds,” Di Maio explained to defense attorney Don West.

Zimmerman also has said he spread Trayvon’s arms apart after the shooting, and investigators found Trayvon with his arms tucked under his body. Bao had testified that he thought it would be unlikely that Trayvon could have moved his arms after the shooting.

•  Trayvon likely was dead within one to three minutes of the shooting. Bao said Trayvon could have been alive and in pain for up to 10 minutes.

•  Zimmerman’s injuries to the back of his head were likely from two impacts, not one as Bao had testified. Another state witness, Dr. Valerie Rao, also had given a lower estimate than Di Maio of the number of times she believed Zimmerman was struck.