Murder is a killing with "malice." "Malice" is a legal term that means a wickedness of disposition, hardness of heart, cruelty, recklessness of consequences, and a mind regardless of social duty, although a particular person may not be intended to be injured. Any strong defense at trial must convince the jury that the Commonwealth has either not proved that you were involved in the killing, or, if you were involved, has not proved that you acted with malice. There are three different classifications of murder in the state of Pennsylvania, which include: 

First degree murder is an intentional killing.

Second degree murder is a killing that is committed while the defendant is committing another felony (such as robbery or burglary). For second degree murder, you can be charged with the killing even if you were just involved in the felony and did not actually commit the killing.

 

Third degree murder is a killing where the defendant does not intend to kill, is not involved in a felony at the time of the killing, but where he still demonstrates "malice." 

Voluntary manslaughter is a killing without malice, where the defendant kills under a sudden and intense passion that results from serious provocation from the person who is killed (or kills someone else by mistake, while trying to kill the provoker).

Voluntary manslaughter is also a killing where the defendant genuinely believes that circumstances are such that, if they existed, would justify him acting in self-defense, but his belief is unreasonable.

Involuntary manslaughter is when as a direct result of committing an act in a reckless or grossly negligent manner, he causes the death of another person.