I think you're misunderstanding what pre-meditation is.
As posted not too far above, a strangulation is pre-meditated (even if the person never thought about it before) because it takes 3-4 minutes to accomplish the murder, and the murderer had time to think it over.
Getting in one's car, starting it and then driving it toward another person is premeditation (even if the murderer didn't think about it even once before letting their foot off the brake and putting it into drive - even if they only meant to scare the other person). That can be just a few seconds.
Beating someone to death is usually charged as first degree for the same reasons as strangulation is.
Going to get a gun, taking it off safety and aiming it at another person, even if the gun user never thought one time of killing that other person, and even if the murderer claims "my finger slipped," is still premeditated murder in most US jurisdictions (and indeed, around the world).
Attempts to cover up one's actions after the fact lead fairly often to first degree convictions.
It doesn't take much. Being a bungling bumbling foolio and messing with a crime scene or trying to hide evidence (but doing it poorly) doesn't remove the premeditation part from the above examples. Most murderers mess up in the aftermath, and if there's any staging or clean-up at all, it is going to be hard for them to say it wasn't premeditated.
Because, you know, if you accidentally strangle your wife or accidentally shoot your gun in the house and it strikes your wife (or whatever), the first thing you do when you realize your "accident" is to call 911. Hiding the body shows a guilty mind and a guilty mind can also be evidence of premeditation. "Gee, I wish she were dead and look, my hands are around her neck!" is the essence of premeditation for most DV cases.