The difference between first degree and third degree felonies is based on the gravity of the crime and the requisite penalties. There are six classes of felonies in state criminal codes.
First degree felonies, the most serious felony charge, carry a possible life prison sentence without parole. In some states, the punishment can be death.
First Degree Felony
First degree felonies are reserved for the most serious of crimes. For example, pre-meditated murder is a first degree felony in every state.
Third Degree Felony
Third degree felonies are less serious. They are still punishable by prison but carry less time. They are almost always eligible for a probationary sentence (assuming the person is eligible based upon their prior record and other factors). Third degree felonies are not punishable by death.
One difference commonly found between these two classifications of felonies is the requirement of mandatory sentencing. With first degree felonies, the sentence of prison time is often mandatory.
Both first degree and third degree felonies are punishable by prison sentence in a state correctional facility.