The condemned are not told until three hours before their execution on the day its going to happen. Most times, the condemned are awakened right before dawn and are dead right as the sun rises. No one speaks to them as they are prepped, walked, and then executed. Total silence.
Quick. Efficient. Clean.
The side benefit is that most on Japan's death row hate going to sleep.
I read on a blog about a Japanese death row inmate who used to scream each time he was awakened from sleep by any noise.