Murder is described at common law as the unlawful killing of a human being with malice aforethought.  Florida, like many other states, has subdivided murder into degrees.  Florida recognizes three degrees or murder, all of which are proscribed in Florida Statute § 782.04.

1st Degree Murder –

The unlawful killing of a human being committed with malice aforethought, or rather perpetrated from a premeditated design to effect the death of the person killed OR any other human being who may be incidentally killed.

When committed by a person engaged in the perpetration of, or the attempt to perpetrate any enumerated felony, or drug trafficking offense prohibited by Florida Statute § 893.135(1)

Enumerated felonies include, but are not limited to:
    Arson
    Sexual battery
    Robbery
    Burglary
    Kidnapping
    Aggravated child abuse
    Any felony that is an act in furtherance of terrorism

Murder in the 1st degree is a capital felony which may be punished by death.
Murder in the 1st degree is simply described as planning to kill someone, and then following through with the plan.

2nd Degree Murder –

The unlawful killing of a human being committed with a depraved mind, which creates an imminently dangerous situation WITHOUT any premeditated design to effect the death of another. When a person is killed in the perpetration of, or the attempt to perpetrate any enumerated felony listed above, or drug trafficking offense prohibited by Florida Statute § 893.135(1)

The primary difference between M1 and M2 is that M2 doesn’t require premeditation.  M2 may be accomplished by sheer stupidity, or a demonstrated indifference to the value of human life.  A good example would be someone who steals a car, and then leads police on a high-speed chase through a densely populated neighborhood.  If the thief were to strike someone with the stolen vehicle and kill them, he would probably be guilty of M2 because while he did actually kill someone, he didn’t plan to do it –the death resulted from the thief’s indifference to human life while committing an enumerated felony.

3rd Degree Murder –

Third degree murder is exactly the same as second degree murder except that it is accomplished while committing any felony which is NOT enumerated above.