I don't understand why any form of execution -- lethal injection, firing squad, guillotine, or any other -- isn't preceded by a hearty dose of morphine.
Remind me again why execution is a valid punishment? And if you think it's valid, isn't reducing pain by morphine as you say going against the reasoning for being a valid punishment?
Punishments are about a combination of rehabilitation, disincentivization and reducing or eliminating harm to society at large. In cases of capital punishment, the chances of rehabilitation is considered to be effectively zero, so the other two factors are emphasized.
Perhaps because the perpetrator's victims didn't get a "hearty dose of morphine" when they were shot, stabbed, raped, buried alive, burned alive or tortured.