What is the legal test for a murder by lying in wait?

The lying-in-wait special circumstance requires proof of the following: " ' " ' "an intentional murder, committed under circumstances which include (1) a concealment of purpose, (2) a substantial period of watching and waiting for an opportune time to act, and (3) ... a surprise attack on an unsuspecting victim from a position of advantage ...." ' " ' " (People v. Woodruff (2018) 5 Cal.5th 697, 774.)

" ' " ' "The element of concealment is satisfied by a showing ' "that a defendant's true intent and purpose were concealed by his actions or conduct. It is not required that he be literally concealed from view before he attacks the victim." ' " [Citation.]' " [Citation.] As for the watching and waiting element, the purpose of this requirement "is to distinguish those cases in which a defendant acts insidiously from those in which he acts out of rash impulse. [Citation.] This period need not continue for any particular length ' "of time provided that its duration is such as to show a state of mind equivalent to premeditation or deliberation." ' [Citation.]" [Citation.] "The factors of concealing murderous intent, and striking from a position of advantage and surprise, 'are the hallmark of a murder by lying in wait.' " ' " (People v. Cage (2015) 62 Cal.4th 256, 278 (Cage).)