How does it make sense that Judges can sentence so differently based on state law?

Watching documentary on murderous women cause reasons... but it goes from woman killed guy with Arsenic with very easy evidence on her gets only 10 years probation yup no prison time.
Meanwhile basically the same case but in another state women is executed. Ain't the difference maddening?


How does it make sense that Judges can sentence so differently based on state law?
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