Smith 'paid his debt tonight' - son of murder victim

Alabama has executed convicted murderer Kenneth Eugene Smith with nitrogen gas, the first time the method of capital punishment has been used globally.

Smith, 58, lost two final appeals to the Supreme Court and one to a federal appeals court, arguing the execution was a cruel and unusual punishment.

The son of Elizabeth Sennet, who was killed by Kenneth Smith, spoke to the media following Smith's execution.

Mike Sennett said he "was glad this day is over" and that Smith had "paid his debt".