Here's a strange one:
A guy went with his girlfriend to her apartment near here so she could retrieve something. He got into an argument with another tenant, who was the girl's previous boyfriend. Neither male had met the other before. The former boyfriend went to his apartment, retrieved his gun, and killed the new boyfriend. He's charged with first degree murder. There seemed to be nothing premeditated about it. I'm assuming the first-degree charge stemmed from the guy going into his apartment to get the gun--if he'd been armed during the argument, it would have been second-degree murder. I think they reached for "first degree" to incent a plea bargain.
Definitions of the degrees of murder vary from state to state. But it is essentially universal that first degree murder encompasses premeditation. The element of premeditation is defined by statute and/or case law. Classic premeditation, supporting first degree, would be lying in wait, poisonings, or making arrangements prior to the killing to escape or cover up the crime.
In Pennsylvania this guy would likely be charged with first degree murder, but, ljust as you suggested, the DA would be likely to accept a plea to third degree. In Pennsylvania premeditation can be be reached in a second, so the fact that the old boyfriend went to his apartment to retrieve a gun could provide a basis for forming an intent to kill.
Another oddity about PA is that our second degree murder is felony murder, which is any killing committed in the course of a felony. It carries a mandatory life sentence. Third degree murder refers to the "hot blooded" murders, not included in first degree.
