Published: Sep 30, 2010 5:17 PM EDT
Updated: Sep 30, 2010 2:17 PM EDT

TALLAHASSEE, Fla. (AP) - A Florida death row inmate who won a stay of execution earlier this year has died of apparent natural causes.

Corrections officials said David Johnston, convicted of killing an elderly woman at her Orlando home in 1983, died early Thursday at Florida State Prison in Starke.

Johnston was 50. An autopsy has been scheduled.

The Florida Supreme Court issued a stay on March 4, five days before his scheduled execution.

The stay was ordered so a hearing could be held on the validity of a new IQ test that could have spared his life by showing he was mentally retarded.

After the hearing a judge ruled he was not mentally retarded. Johnston's appeal of that decision was pending in the Supreme Court when he died.