What is the test for a charge of assault against a police officer under the California Civil Code of Criminal Procedure 2651?

performance of his or her lawful duties. Lawfulness of the arrest is an essential element of this offense. (See CALCRIM No. 2651 ["To prove that the defendant is guilty of this crime, the People must prove that: [] 1. The defendant willfully and unlawfully used (violence/ [or] a threat of violence) to try to (prevent/ [or] deter) an executive officer from performing the officer's lawful duty; AND [] 2. When the defendant acted, (he/she) intended to (prevent/ [or] deter) the executive officer from performing the officer's lawful duty." (Italics added.)].) "[I]t is . . . a 'well-established rule that when a statute makes it a crime to commit any act against a peace officer engaged in the performance of his or her duties, part of the corpus delicti of the offense is that the officer was acting lawfully at the time the offense was committed.' " (People v. Cruz (2008) 44 Cal.4th 636, 673.)