Miami's John Errol Ferguson, convicted of murdering eight people in the 1970s, will be executed by lethal injection at 6 p.m. Tuesday., state corrections officials announced.

The announcement Thursday came one day after the Florida Supreme Court upheld a trial judge's decision ruling that Ferguson, 64, was legally competent to be executed.

Defense attorneys have maintained for decades that Ferguson is severely mentally ill and his execution would be “cruel and unusual punishment.” They are appealing to the U.S. Supreme Court.

Ferguson was convicted of the July 1977 murders of six Carol City residents during a home-invasion robbery. At the time, it was the worst mass murder in Miami-Dade history.

Ferguson, now 64, also was convicted separately of murdering two teenagers, Belinda Worley, a 17-year-old Hialeah High School senior, and Brian Glenfeldt, 17, in January 1978.