Thanks to some who emailed me, it appears that Illinois is an outlier in its first degree murder laws.
In order to prove that the defendant committed first degree murder, the prosecutor must show beyond a reasonable doubt that the defendant killed an individual without lawful justification and either:
* Intended to kill or do great bodily harm to that individual (or knew that the act would do so); or
* Knows that the acts create a strong probability of causing death or great bodily harm to the individual; or
* The defendant was attempting or committed a forcible felony other than second degree murder (i.e. rape).
In other words the prosecutor has an easier job here than she would in most states. It seems pretty self-evident that Jason Van Dyke meant to kill Laquan McDonald. I still think the highest murder charge is potentially overkill in this case, but at least the state does not have to prove premeditation.