In sum, the Kazalyn instruction and Powell and its progeny do not do full justice to the phrase "willful, deliberate, and premeditated." Deliberation remains a critical element of the mens rea necessary for first-degree murder, connoting a dispassionate weighing process and consideration of consequences before acting. "In order to establish first-degree murder, the premeditated killing must also have been done deliberately, that is, with coolness and reflection." Brown, 836 S.W.2d at 539; see also LaFave & Scott, Criminal Law § 7.7(a), at 643.
Because deliberation is a distinct element of mens rea for first-degree murder, we direct the district courts to cease instructing juries that a killing resulting from premeditation is "willful, deliberate, and premeditated murder." Further, if a jury is instructed separately on the meaning of premeditation, it should also be instructed on the meaning of deliberation.[3]
Accordingly, we set forth the following instructions for use by the district courts in cases where defendants are charged with first-degree murder based on willful, deliberate, and premeditated killing.
Murder of the first degree is murder which is perpetrated by means of any kind of willful, deliberate, and premeditated killing. All three elements willfulness, deliberation, and premeditation must be proven beyond a reasonable doubt before an accused can be convicted of first-degree murder. Willfulness is the intent to kill. There need be no appreciable space of time between formation of the intent to kill and the act of killing. Deliberation is the process of determining upon a course of action to kill as a result of thought, including weighing the reasons for and against the action and considering the consequences of the action. A deliberate determination may be arrived at in a short period of time. But in all cases the determination must not be formed in passion, or if formed in passion, it must be carried out after there has been time for the passion to subside and deliberation to occur. A mere unconsidered and rash impulse is not deliberate, even though it includes the intent to kill.[4] Premeditation is a design, a determination to kill, distinctly formed in the mind by the time of the killing. Premeditation need not be for a day, an hour, or even a minute. It may be as instantaneous as successive thoughts of the mind. For if the jury believes from the evidence that the act constituting the killing has been preceded by and has been the result of premeditation, no matter how rapidly the act follows the premeditation, it is premeditated. The law does not undertake to measure in units of time the length of the period during which the thought must be pondered before it can ripen into an intent to *715 kill which is truly deliberate and premeditated. The time will vary with different individuals and under varying circumstances. The true test is not the duration of time, but rather the extent of the reflection. A cold, calculated judgment and decision may be arrived at in a short period of time, but a mere unconsidered and rash impulse, even though it includes an intent to kill, is not deliberation and premeditation as will fix an unlawful killing as murder of the first degree.