What is the test for proving intentional killing?

To prove a killing was willful, deliberate, and premeditated, the prosecutor is not required to prove a defendant "maturely and meaningfully reflected upon the gravity of his or her act." (Former 189, 4th par.) "'An intentional killing is premeditated and deliberate if it occurred as the result of preexisting thought and reflection rather than unconsidered or rash impulse.' [Citation.] The reflection may be arrived at quickly; it need not span a specific or extended period of time." (People v. Lopez (2018) 5 Cal.5th 339, 354-355.)

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