Miss Santos does not dispute the facts in the case. What we are arguing is the cause. For this to be considered a crime, we need more than the fact that it happened. We also need to determine why. To determine that a person has committed a crime, we have to know that he or she had the intention of committing that crime. If you commit a crime, you do so by making a choice, which implies that you have free will. If you do not have free will, you should not be held responsible for your actions, even horrific actions.
You probably recognize this in the idea of insanity. If a person is insane, we do not hold him or her legally responsible because we know they do not understand the meaning of their actions. If we punished them, they would not understand what it was for, either, but just as much as this is true, we do not punish the insane because we know it would be cruel. Punishment is not revenge. Our system does not include the idea of revenge. It is intended to achieve justice, not vengeance, and this means that the person being punished understands why.
A person who is insane is subject to what philosophers call determinism, because his choices are being made by a mental defect, a disease, and not by choice. There are other conditions as well that can determine our actions so that we are not responsible for what we do. One of these is an extreme case of PMS, which alters the body chemistry of the woman suffering from it and which affects her mental and emotional condition as well. This is a powerful force that has developed during them course of her lifetime. If she had understood what was happening to her, she might have sought help and prevented it. But since she did not understand what was happening to her, it slowly changed her and came to control her actions.
You might say she should have known, but we all have conditions that develop until we recognize the symptoms. When we do, we get help. Before ...