An 81-year-old inmate who was the “longest serving resident of South Carolina’s Death Row” died of natural causes this week, officials said. 

Fred Singleton passed away Monday at the Kirkland Correctional Institution’s infirmary, the South Carolina Department of Corrections announced on Friday. He was sentenced to die in 1983 for raping and strangling a woman in Newberry County and stealing her jewelry, according to court records. 

Singleton spent his last three decades in prison in legal limbo after the state Supreme Court ruled he wasn’t competent to be executed because he didn’t understand he could die in the electric chair and only answered questions from his attorneys with “yes” or “no,” according to The Associated Press. 

However, the justices also decided in 1993 that Singleton’s death sentence should remain in case advances in psychology allowed him to get better and that he couldn’t be forced to take medication to improve his mental state only so he could be executed, the AP added. 

Brad Sigmon was convicted of beating to death his estranged girlfriend’s parents in Greenville County in 2001. He was executed by firing squad in South Carolina earlier this year. (South Carolina Department of Corrections via AP)

There are now 24 men remaining on South Carolina’s death row after Singleton’s death.

There have been two firing squad executions in South Carolina this year. 

In early March, Brad Sigmon, a 67-year-old who was convicted of killing his ex-girlfriend’s parents with a baseball bat in 2001, was executed by firing squad for the first time in 15 years in the U.S. 

A South Carolina Department of Corrections officer sits inside a control room at Kirkland Correctional Institution on March 14, 2019, in Columbia, S.C. (Tribune News Service/Getty Images)

The following month, Mikal Mahdi, 42, was put to death by the same method. He was convicted in the 2004 killings of an off-duty police officer in Calhoun County in South Carolina and a convenience store clerk in Winston-Salem, North Carolina. He was sentenced to death for the murder of the officer and life in prison for the clerk’s murder.