The activists said John McNeil’s conviction was proof that self-defense laws, which McNeil cited in his 2006 trial, are not applied equally to all races in the United States. McNeil is serving a life sentence for the 2005 shooting death of Brian Epp, whom he had hired as a contractor on his Kennesaw home.

“Something is wrong here. Morally wrong. Legally wrong,” said the Rev. William Barber II, an NAACP national board member and president of the group’s North Carolina chapter. “And the only thing that will make it right is to free John McNeil.”

Civil rights organizations have criticized the case since McNeil’s arrest almost nine months after the shooting. Cobb County District Attorney Pat Head pursued a murder charge despite the conclusion of Kennesaw police detectives that McNeil committed no crime. Head won a jury verdict that the Georgia Supreme Court upheld in 2008.

A second appeal awaits action by a trial court in Baldwin County, where McNeil was first imprisoned. He has since been moved to Macon State Prison in Oglethorpe.

A spokeswoman in the Georgia Attorney General’s office, which is fighting the second appeal, declined to comment, citing office policy not to talk about pending cases. Through a spokeswoman, Head said Monday, “As far as we are concerned, this case is over and done.”

Barber and his Georgia counterpart, Edward DuBose, said Monday that the case has gained new urgency because McNeil’s wife, Anita, has been diagnosed with cancer. The case also has reclaimed the spotlight since the killing of Trayvon Martin in Florida. Prosecutors there initially declined to charge a multiracial Hispanic man, George Zimmerman, with a crime after he shot Martin, an unarmed black teenager. Zimmerman is now charged with second degree murder.

“We are victims at both ends of the gun,” said Marcus Coleman, who leads the Atlanta chapter of the National Action Network.

McNeil never denied that he shot Epp, but told Kennesaw police that the victim was belligerent and, after wielding a knife during an altercation with McNeil’s son, charged at the elder McNeil. Investigators found a knife on Epp. An eyewitness testified that he saw Epp charge McNeil but did not see a knife. The eyewitness confirmed McNeil’s account that he fired a warning shot.

NAACP President Benjamin Todd Jealous said his organization questions “stand-your-ground” laws that do not require a person, regardless of their location, to retreat from a perceived threat if they have an opportunity. But, Jealous said, “we have no qualms about the Castle Doctrine,” which governs threats that occur on personal property.

McNeil’s conviction in the face of that doctrine, Jealous said, means that in Georgia, “When it comes to protecting your home and your family, there is no law that can protect a black man from a biased system of justice.”

Atlanta attorney Mark Yurachek is handling McNeil’s second appeal. Yurachek argues that McNeil’s trial attorney made several errors that denied him a fair opportunity for exoneration.

Should that appeal ultimately fail, McNeil’s next opportunity for freedom would be a clemency request to the Georgia Board of Pardons and Paroles. Yurachek said he is not optimistic about any hearings in front of that body, though Barber and Jealous said the NAACP planned to mount a public campaign.

Jealous said he is reaching out to gun-rights organizations — he declined to name the National Rifle Association or any other group — to build public support for McNeil outside the civil rights community. “Any defender of gun rights and property rights should care about this case,” he said.

Jealous added that he would discuss the case with Gov. Nathan Deal, who appoints Pardons and Paroles board members.