The day after Troy Davis was executed for the 1989 murder of a Georgia police officer, his family and supporters vowed to continue their fight against the death penalty.

His sister, Kimberly Davis, told ABC News on Thursday that Troy had urged his family to fight on behalf of future death-row inmates whose guilt was in doubt.

This fight didn't start with him and it's not going to end with him, Kimberly Davis said.

Kathryn Hamoudah, the leader of the Atlanta chapter of the anti-death penalty organization Georgians for Alternatives to the Death Penalty, expressed similar sentiments in an interview on Wednesday night with Amy Goodman of Democracy Now.

Many people have woken up because of this case, and we hope people will stay awake and continue to fight, Hamoudah said.

Davis' case drew a tremendous outpouring of support from around the world as people protested Georgia's decision to execute him in spite of the fact that seven of the nine original witnesses who testified against him had later recanted part or all of their testimony.

'Too Much Doubt' Surrounding Conviction

His supporters' argument was not so much that Davis was innocent, but that there was too much doubt surrounding his conviction to justify the death penalty. His lawyers appealed to several state and federal courts to commute Davis' sentence to life in prison without parole, but one court after another refused to grant clemency.

Davis maintained his innocence to the very end. In a brief statement just before he was executed, he said, I'd like to address the MacPhail family -- let you know, despite the situation you are in, I'm not the one who personally killed your son, your father, your brother. I am innocent.

The family of Mark MacPhail, the Savannah, Ga., police officer who was murdered in a Burger King parking lot in 1989, said they had no doubts that Davis was guilty. They expressed relief that he would finally be executed after 22 years and three stayed execution dates.

I will grieve for the Davis family because now they're going to understand our pain and our hurt, Joan MacPhail-Harris, Mark MacPhail's widow, told The Associated Press on Wednesday. My prayers go out to them. I have been praying for them all these years, and I pray there will be some peace along the way for them.

Kimberly Davis told ABC News that she and her family last saw Troy between 11 a.m. and 3 p.m. on Wednesday, several hours before he was scheduled to be executed by lethal injection, and that he seemed at peace.

The execution ended up being delayed for about four hours while the U.S. Supreme Court reviewed a last-minute appeal from Davis' lawyers. Hundreds of supporters waited outside the Georgia Diagnostic and Classification Prison in Jackson, Ga., holding their breath and praying that the court would stay the execution. But the court rejected Davis' appeal around 10:30 p.m., and he was pronounced dead at 11:08.

When we left my brother yesterday, my brother told us to hold our heads up and be strong because if the state of Georgia did succeed in executing him, they would only take his physical body and not his soul, Davis said. My brother said he only wanted to be a free man, and right now, he is free.