What is the test for establishing that a police interview was not custodial?

That the patrol car interview was not custodial is clear. Defendant's participation was requested and readily given. The location was chosen because the alternative, defendant's residence, was cold and dark; defendant himself agreed it was not suitable. No indicia of arrest were present. Defendant was neither searched nor handcuffed. No evidence indicated he knew the car doors were locked, and the windows were closed only at his request; later a back door was opened, and defendant partly exited to smoke a cigarette. The interview itself was short, and the questions focused on information defendant had indicated he possessed rather than on defendant's potential responsibility for the crimes. Nothing in the interview or its circumstances, in short, would have led a reasonable person to think he was not free to end the questioning and leave. (People v. Leonard, supra, 40 Cal.4th at p. 1400.)

B. Conversation en Route to Sheriff's Station