I can think of about 5 solid reasons and five decent ones as to why he should not be executed.  But not doing it because that is what he wants is silly and downright inhumane.  

No one has the right to not let someone end their own life.  From the cancer patient who had to move to Oregon to end hers, to the force feeding at GITMO, it's inhumane force some one to remain alive that does not want to.

  Other cases involved defendants who, while competent and criminally responsible by legal standards, suffered from severe  mental illness. The only thing I have heard in this case which is even suggestive of impaired capacity is that he voluntarily smoked a lot of marijuana. That is unlikely to register with jurors  to the same extent.

  Also, Ted Kaczynski, Jared Loughner and Eric Rudolph  were all  spared by virtue of  plea agreements not a jury verdict. With Kaczynski and  Loughner, no  doubt the government was influenced by the fact both were  deemed  paranoid schizophrenic. Rudolph might present the closest parallel to this case as he appears to have been motivated by political extremism rather than compelled by mental illness, but again, that was a plea agreement not a jury deciding he should not receive the death penalty.

  Susan Smith was spared by a jury but was able to present compelling expert evidence of mental illness (and she was a white American woman which while not a "legitimate" factor is a real world factor). I might be wrong, but I believe that is the only case where Clarke "won" a life sentence for  a defendant convicted of a DP eligible murder. As I recall  Moussaoui is the only other jury verdict, and he didn't actually kill anyone (he was a member of a conspiracy which resulted in murder so was found DP eligiblke) He pleaded guilty but did not have a deal taking the DP out so there was a sentencing before a jury and Clarke did convince the jury to go for LWOP.

After a federal trial in 1997, Nichols was convicted of conspiracy to use a weapon of mass destruction and eight counts of involuntary manslaughter for killing federal law enforcement personnel.[7][8] He was sentenced to life imprisonment without the possibility of parole because the jury deadlocked on the death penalty.[6] He was also tried in Oklahoma on state charges of murder in connection with the bombing. He was convicted in 2004 of 161 counts of first degree murder, including one count of fetal homicide;[6] first-degree arson; and conspiracy.[9] As in the federal trial, the state jury deadlocked on imposing the death penalty.[6][10] He was sentenced to 161 consecutive life terms without the possibility of parole,[2][6] setting a Guinness World Record[11] and is incarcerated at ADX Florence, a super maximum security prison near Florence, Colorado. He shares a cell block that is commonly referred to as "Bombers Row" with Ramzi Yousef and Ted Kaczynski.

But there is a lot about this case that raises questions and makes one wonder if we're getting the whole story.  

There have been conspiracy theorists from the beginning - many of whom got into the false flag, crisis actor, meme that was widely disseminated and which made those people sound like complete idiots - and cruel and callous ones at that.  To claim that Martin Richard and his family were faking their injuries is beyond cruel and beyond ridiculous.  

But now we have journalists who write for mainstream publications like the Washington Post and the Boston Globe also asking questions - finally.  Whether the defense should raise these issues and attempt to create doubt about the official story, I don't know.  I don't know if Judge O'Toole will allow it.  But if I were trying to save this kid's life, I think I would pull out all the stops.