don't think the burden of proof is that they thought someone could die, rather that they committed a felony and someone died as a result of it.
Edit: Apparently I am not correct. Though the letter is as I say, application tends to lean on "dangerous acts." In this case though, attacking someone with a knife should qualify as a "dangerous act" which could forseeably cause a death.
As far as CO is concerned, you had it right the first time. One of the more recent cases was a women (Lisle Auman) and some friends who had committed B&E and were caught in the act by police. A chase ensued, in which Auman's group fired at police officers. The chase ended and Auman was taken into custody, but one of the group shot an officer, and she was convicted of felony murder. Lisl Auman's conviction was overturned after 5 years, though, as "the jury instruction on the predicate second-degree burglary charge was improper".
Most people felt that it shouldn't apply as she was already handcuffed in the cruiser when her friend shot the officer. But that wasn't what got her off, and the Supreme court upheld that being in police custody does not preclude the statute. I tend to side with "most people" on that one; she had already surrendered and thus was no longer engaged in felonious activity, which should have removed culpability for felony murder.
But barring such unusual and extreme cases as hers, I agree with the felony murder stautes. While it pushes the boundaries of the 8th amendment, it is a very strong deterrent. I do, however, believe that felony murder should be classified as murder two, not one, as the unintended death certainly doesn't constitute premeditation. But murder two is appropriate, as the death would not have occured if the felony had no been committed.
Law abiding citizens have nothing to fear from it. So long as you don't commit a felony, you won't have to worry about felony murder charges.
We in the firearms community constantly argue that there wouldn't be a problem with gun crime if the justice system didn't turn dangerous individuals loose on society. Felony murder is one of the few laws that gaurantees they won't. Is it a really harsh punishment? Absolutely. Will it make people think twice about committing armed robbery and the like? Most definitely.
I feel that it provides almost as much deterrence from violent crime as armed citizens do. Only problem is that many offenders don't know of felony murder's existence until they're convicted of it.