Bitterly cold weather prompted death penalty opponents to cancel a news conference to discuss efforts to halt executions.
The news conference had been scheduled for noon Monday at the Missouri Capitol.
George Mercer was executed on Jan. 6, 1989, for the 1978 rape and slaying of waitress Karen Keeten in the Kansas City area. Mercer's execution was Missouri's first after a nationwide moratorium on capital punishment was lifted in 1976.
Since then, Missouri has executed 70 inmates.
The state executed two people in the past two months and is scheduled to execute Herbert Smulls on Jan. 29 for the 1991 robbery and slaying of suburban St. Louis jewelry store owner Stephen Honickman.