Two of our clients who were charged with murder are successfully serving sentences of community supervision. How is that possible? Because it was the right sentence for both clients given the facts, the circumstances, and their role in each unrelated offense.
If a person convicted of murder has never previously been convicted of a felony, the jury can choose a sentence from a $1.00 fine to life in prison. After hearing all the facts, the jury has the power to decide that while a person may not have been legally entitled to a self-defense claim, he certainly doesn't belong in prison. Similarly, a jury may feel that a defendant's violent criminal history is so disturbing that he should be sentenced to prison for decades.
Sentencing decisions in murder cases often find their basis in religious, moral, and retributive grounds.