James Phillip Barnes was born on March 7, 1962. He was one of five siblings and had a twin sister named Jeannice. Barnes had a younger brother, Michael, who sadly committed suicide. Although the exact location of his birth is not known, Barnes referred to his home as Maryland.

On April 20, 1988, James Phillip Barnes entered the home of Patricia "Patsy" Miller in Melbourne, Florida. He came in through a bedroom window and confronted her with a knife. Barnes assaulted Patricia before attacking her with a hammer. He bound her with shoelaces while she was lying on the bed. After killing her, he set her bed on fire in an attempt to hide the evidence and fled the scene. Patricia’s death was later ruled a homicide caused by blunt-force trauma, and the case went unsolved.

On December 11, 1997, Barnes killed his estranged wife, Linda Barnes, at her home in West Melbourne. He had a restraining order against him that prohibited him from being near her. After he strangled Linda, he concealed her body in a closet and remained in the house until law enforcement arrested him the next day and charged him with murder.

In 1998, Barnes pled guilty to the murder of Linda and received a life sentence without the possibility of parole. In 2005, while in prison, he confessed to the murder of Patricia Miller. He wrote a letter to an assistant state attorney during Ramadan, stating that he wanted to clear his conscience. He admitted to the crime to avoid any witnesses against him.

After his confession, Barnes was tried for the murder of Patricia Miller. He chose to represent himself during the proceedings. In 2006, he pled guilty to first-degree murder, burglary, two counts of sexual battery with a weapon, and arson. The judge sentenced him to death in December 2007.

In 2010, while still on death row, Barnes gave an interview to filmmaker Werner Herzog. He later confessed to the murders of Chester Wetmore and Brenda Fletcher in a letter sent to Herzog. He claimed responsibility for these deaths but was never charged in those cases.

On June 22, 2023, the governor of Florida signed Barnes’s death warrant. He was scheduled to be executed on August 3, 2023. In a hearing before his execution, Barnes accepted responsibility for his actions and did not request any delays. On the day of his execution, he declined a last meal and visitors. At 6:13 p.m. on August 3, 2023, Barnes was pronounced dead after receiving a lethal injection at Florida State Prison. He did not make a final statement.