Columbia, South Carolina - A South Carolina man convicted of murder is scheduled to be put to death by lethal injection on Friday, the first execution in the US this year.

Marion Bowman Jr. (44) was sentenced to death in 2002 for the murder the previous year of Kandee Martin (21) a high school friend.

Martin was shot to death and her body placed in the trunk of her car, which was set on fire.

Bowman, who was 20 years old at the time, has acknowledged that he sold drugs to Martin but denied any involvement in her murder.

"I am so sorry for Kandee and her family, but I did not do it," he said in a statement posted online by his lawyer. "I just don't want to be executed or imprisoned for life for a crime that I didn't commit."

Bowman has filed numerous appeals seeking to put off his execution, including a claim that the attorney who defended him at trial "held racist attitudes."

Bowman is Black. Martin was white.

Bowman's attorneys also argued that two witnesses who testified against him and received plea deals suffered from "credibility issues."

Bowman has also sought to halt his execution because of the possibility of complications stemming from his body size – he weighs nearly 400 pounds.

This exposes him to the danger of a "potentially torturous execution process," his lawyers said.

Bowman's appeals have all been denied, and he is to be put to death at 6:00 PM at a prison in Columbia, the state capital.

The judge who denied Bowman's appeal over concerns about lethal injection said he could have opted for the electric chair or the firing squad instead.

There were 25 executions in the US last year. Three used the controversial method of nitrogen gas, while the rest relied on lethal injection.

Four more executions are scheduled over the next two weeks, including two in Texas.