Section 565.020 defines a single offense of first- degree murder with the express range of punishment including life imprisonment or death. Section 565.030 delineating trial procedure in cases of first-degree murder does not create, or differentiate, two separate categories of first-degree murder offenses. The maximum penalty for first-degree murder in Missouri is death, and the required presence of aggravating facts or circumstances to result in this sentence in no way increases this maximum penalty (Apprendi v. New Jersey).