No. He should not. His mental condition was too obvious to argue against other reasonable causes of capital punishment. He did it accidentally, and if he had been more sound of mind, this may have not happened. All that Lennie needs is to be confined and put away, because his lack of mental capacity has become a burden; not because he CHOOSES to be a burden.
I think that you will find a variety of answers to this particular question. It is difficult, in general, to establish intent to the point where death is the ultimate punishment. It becomes even more difficult for someone who is challenged mentally. I think it says something fairly terrible when a state executes someone who is mentally challenged. At the same time, what makes Steinbeck's work so powerful is that we, as the reader, could not in good conscience sentence Lenny to die. In being given a privileged and interior view of Lenny and his motivations, how would we be able to conclusively say that he should die. We understood what happened and possessed the full understanding behind the action. Perhaps, this is what makes the issue of the death penalty so compelling and so difficult. If we were able to clearly establish "what happened," these mitigating circumstances might prevent us from issuing a pronouncement of death, in general.
In Lennie's particular case, I do not think he deserved to die, at least not the way the story tells it.
For someone to deserve to die, they must at least intend to kill their victim, in my opinion. The narrator of the story makes it clear that Lennie did not intend to kill Curley's wife. It was really just an accident brought on by Lennie's strength and lack of intelligence. So to me, it's not a matter of being mentally challenged, it's the fact that he didn't intend to kill her that means he does not really deserve to die.
Lennie accidentally kills Curely's wife in the story "Of Mice and Men. " There are several types of murder charges; intent to kill that includes some degree of planning must be proven for him to be tried for first degree murder, and second degree occurs when someone willfully kills someone in the heat of the moment.
The justice system that was around during Lennie's lifetime had not advanced in regards to Human Rights as much as it has now a days. Lennie had no protection under the law. Under today's law it would have to be proven to have intended to kill Curley's wife. He could still be tried unless through psychological examination they found him unfit to stand trial. Even though as a reader one may like Lennie and identify his innocence, he still has a penchant for hurting animals and does not have an understanding of his own strength. He is a danger to society.
No one would look away from George's mercy shooting either. George would have been tried on first degree murder charges and probably be found guilty irregardless of his reasons for killing Lennie.
I believe that Lennie would be more of a candidate for long term mental hospital placement. One can not reform someone if the level of understanding is not present. However, Lennie demonstrates that he can not be alone with animals or females even if he only wants to touch.
I wouldn't compair Lennie to an animal, so I don't think he should have been killed out of mercy. No one should ever have to kill another human being out of mercy. He would have been shot by Curley right away. It seemed that way from the way of the story.