Leavitt, 53, made no final statement, KBOI-TV in Boise reported. The television station, which had a reporter witness the execution, said the condemned man appeared calm throughout the procedure.
In his final days, Leavitt continued to deny killing Danette Elg, 31, of Blackfoot in 1984. She was found in her home, stabbed many times and with her genitals mutilated.
A court ruled last week in a case brought by several news organizations that witnesses should be able to see the entire execution procedure. Idaho corrections officials had planned to insert lines for intravenous drugs before opening the curtains.
Leavitt is only the third man to be executed in Idaho since the state adopted a death penalty law in the 1970s. An inmate who waived his appeals was put to death in 1994, and Paul Rhoades was executed in November.
The state currently has 11 men and one woman under sentence of death.
About 30 people gathered outside the prison to protest the execution.