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. 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 thinks out the act, no matter how quickly—it can be as simple as deciding to pick up a hammer that is lying nearby and 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 the fact that a defendant was excited or angry doesn't rule out deliberation.
All that 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 seconds, as long as the thought process occurs before the act.
No specific formula exists 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 had 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. 2009).)
The most common use of "premeditation and deliberation" is to distinguish between different grades of murder. First-degree murder often requires proof that the killing was premeditated and deliberate (that is, a cold-blooded killing). Second-degree murder is an intentional killing (i.e. impulsive, yet intentional, killing). Critics argue this "time" distinction isn't really a distinction at all if premeditation and deliberation can take but a moment.