malice aforethought

Definition from Nolo’s Plain-English Law Dictionary

The state of mind necessary to prove first-degree murder. The prosecution must prove that the defendant intended to cause death or great bodily harm, or exhibited extreme and reckless indifference to the value of life. Any intentional killing that does not involve justification, excuse, or mitigation is a killing with malice aforethought.

Definition provided by Nolo’s Plain-English Law Dictionary.