I dont agree with the lethal injection or any other type of capital punishment for two reasons..
1) why should he get off with it so easily, his suffering stops the second he is dead. keep him alive in solitary confinement for the rest of his natural...
2) Apparently, it works out far more expensive to execute someone than to keep them in prison for the rest of their life, due to the appeals etc. according to a USA site I read on the subject some months ago.