There are plenty of criminals for whom the death penalty is the right penalty. Whether it is the right penalty for Andrea Yates is a much harder call. If she is spared capital punishment, it should not be because she is a woman and not because the death penalty is too much for those who confuse squeamishness with higher morality.
The record of her previous irrationality could raise a reasonable doubt as to whether she acted rationally when she drowned her children. But reasonable doubt is the standard that applies when deciding guilt, and the jury has already made that decision. At the penalty phase, it is no longer just a question about Andrea Yates, but also a question about other potential Andrea Yateses out there who need a loud and clear message that you are not to make such terrible decisions as she did.
A death penalty would say that what the law says is wrong matters a lot more than what you personally think is wrong. There has already been too much bending of the law to allow for individuals' personal notions or cultural habits. There is no point having law if everyone is going to be his own Supreme Court.
No matter whether the death penalty is imposed or not imposed in this case, it is a very tough call -- and those of us who were not in the courtroom when this tragic case unfolded should be grateful that we do not have the terrible weight of responsibility to make that call. Whatever decision is made by those who do have that responsibility should be respectfully considered. This is not some contest where we cheer for our side and boo the other side. This is the tragedy of the human condition for all concerned.