In the US, they want to save 59-year-old Richard Moore from the death penalty on November 1.
Moore was sentenced to death for attempting to rob a convenience store in 1999.
According to investigators, he came to a store in Spartanburg, South Carolina, unarmed and attempted to rob a store clerk, the Associated Press reports.
The man pulled out a gun and pointed it at Moore, and a fight ensued.
During the conflict, Moore took the gun from the seller.
The shopkeeper, trying to defend himself, shot at the robber and wounded him in the arm. The attacker also returned fire, which killed the shopkeeper.
The defendant's lawyers and supporters say he did not receive good legal representation at his first trial in 2001.
Moore claims it was the salesman who initiated the fight.
There were no cameras in the store, so all information about the incident is based on the accounts of the arrested person and the witness.
More than 50 people, including a former judge and a former prison director, are campaigning to overturn the death penalty.
They believe the robbery was not armed and that Moore used the gun for protection.
