What is the test for a special-circumstance felony murder?

strict 'causal' or 'temporal' relationship between the 'felony' and the 'murder' " and "extends even to the situation in which the 'murder was committed while the defendant was engaged in... the immediate flight after committing' the felony"].) The felony-murder special-circumstance finding must be "based upon proof that the defendant intended to commit the underlying felony separately from forming an intent to kill the victim." (People v. Rundle, supra, 43 Cal.4th at p. 156.)