Most states require premeditation, and many also require deliberation, for a conviction of first degree murder. The concepts are intricately related, and the difference between them can be largely semantic. (Other crimes involving a victim's death don't require premeditation and deliberation—for examples, see Homicide: Murder and Manslaughter.) Crimes other than those involving homicide may also require premeditation and deliberation.
Someone premeditates a crime by considering it before committing it. Premeditation requires that the defendant think out the act, no matter how quickly—it can be as simple deciding to pick up a hammer that is lying nearby and to use it as a weapon.
A defendant deliberates by considering the act and its consequences (but not necessarily the punishment), and deciding to follow through with it. A deliberate act isn't provoked or carried out in the heat of passion. But that a defendant was excited or angry doesn't mean that she didn't deliberate.
Time alone doesn't determine whether a defendant premeditated and deliberated. All premeditation and deliberation require is the time it takes to form the intent, ponder the crime, and then act. Defendants can premeditate and deliberate in a matter of minutes, as long as the thought process occurs before the act.
There is no specific formula for determining whether a defendant premeditated and deliberated before acting. Courts and juries will consider the circumstances of each case.
EXAMPLE: A defendant convicted of first degree murder for strangling a victim with a lamp cord premeditated the murder. The evidence showed that the defendant repositioned the cord around the victim's neck numerous times, each time giving him the opportunity to reflect on his actions. The defendant had also had time to consider his actions during a struggle with the victim prior to the strangulation, further proving premeditation. (Berube v. State, 5 So.3d 734 (Fla. 2nd DCA 2009).)