It might be a difference in the law in the different states, then. In FL, TX and UT, first-degree murder/equivalent has been explained to me as "premeditated," meaning "planned." Sure, you can plan in the space of seconds, but it doesn't normally happen.
And about the manslaughter thing, yeah, I explained it wrong. Mike's right.
EDIT: I went and looked at the actual laws; in Florida, that's the case; in Utah, not so much; and in Texas, it'd be murder and not capital murder.
EDIT2: The California Penal Code articles 187 and counting address murder. They make my head hurt, and I have yet to find the end of the damn things. It's probably somewhere around section 200.