The second possible interpretation of Carroll is that, while no time is too short to premeditate, premeditation is still not the same thing as intent to kill.
His conviction of first degree murder was reversed on the ground that, although he had ample time to premeditate and deliberate, he did not have the capacity to premeditate--in other words, to reflect calmly on his intended act.
96) He had the time to premeditate but not the capacity.
The court was careful to distinguish between the amount of time needed to form an intent to kill and the time needed to premeditate.
Juries have discretion to determine how long is long enough to premeditate, when the evidence is sufficient to say that the defendant subjected his decision to a sober second look, when there is enough evidence of coolness, or planning, or a calculated manner of killing.