You people need to become informed of some of the laws of this country before flying off the handle and accusing people of eating paint chips.
When dealing with criminal insanity you should be aware of what are called the M'Naghten Rules, established after a murder in England in the 1840s and named after defendant Daniel M'Naghten. The text is this...
to establish the defense of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind as not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong.
This is to say, when he punched the baby, he didn't know what he was doing, or that it was wrong.
This is easily applicable to a case such as this, It basically says he belongs in an institution to get help not in a regular prison population for punishment. Now don't think that an institution is better than prison, because in many cases you will spend more time in the institution than you would have in prison, and in no cases, less time than how long you would in prison.
To understand what that means - you have to consider 2 different scenarios.
1. A guy murders his wife to collect on life insurance.
-This is a person who is aware what they are doing, and decides that he is willing to do something that is wrong because he will benefit from it.
2. Someone loses control and punches someone and accidentally kills them.
-This is a very different crime than the other example. People should not be executed for this. People getting executed for that is why many people are against the death penalty altogether. I wouldn't say I'm against death penalty but I'd reserve it for people who at the very least kill for benefit to themselves.
Unfortunately people look at situations like punching a baby to death over pulling some cords out, and they can understand the person less than someone who kills their boss for passing them up on promotion. The person did something that makes no sense because the person lost control of themself. You don't decide one day to murder your baby and ruin your own life to avenge an infant pulling at cords. It just happens.