Virtually all of them are convicted in state courts and under state sentencing systems. Most states have mandatory minimums for 1st degree murder, and those minimums are much higher than Holmes' sentence; second-degree murder usually admits a huge range of sentences, which captures the variety of circumstances that might attend an unplanned killing.

"Virtually" - is murder even a federal crime in the United States?

> "Virtually" - is murder even a federal crime in the United States?

Yes, but the general federal murder law (18 USC § 1111) only applies in the “special maritime and territorial jurisdiction of the United States”.

A lot of federal felonies have, in place of a general federal felony murder rule, a distinct crime or enhanced punishment when death is involved and deliberately killing certain federal officials is also a federal crime.

Yes, it is. For instance, if you deliberately murder a senator. 18 USC 111.

I think a bunch of different kinds of federal crimes (like major drug crimes) will also port their accompanying murder charges to federal court.

Many things can move murder to federal court (hence, "make a federal case of it") including crossing state lines and various other federal offenses.

> And there are people in prison doing less time for murder.

Especially if it's perpetrated with a car.