There is no per se custody rule that dictates the giving of Miranda warnings (Miranda v. Arizona (1966) 384 U.S. 436). In determining whether an inmate is in custody for the purpose of requiring a Miranda admonishment, the following factors are considered: whether the language summoning the defendant from his prison lodging was coercive; whether the physical surroundings of the questioning were unduly coercive; whether the defendant was confronted with evidence of guilt; whether there was an opportunity given to the defendant to leave the site of questioning. (Cervantes v. Walker (1978) 589 F.2d 424, 427-428; People v. Roldan (2005) 35 Cal.4th 646, 736.) In this case, defendant Macklem, imprisoned and awaiting trial for the murder of his friend, assaulted a fellow inmate and was moved to a more secure facility. Prior to being interviewed by a detective, Macklem was asked if he wished to come out and talk but was told he need not do so; Macklem was advised of the purpose of the interview, i.e, an investigation as opposed to being confronted with clear evidence of guilt; the interview took place in the attorney/doctor visiting room with the door ajar and Macklem unhandcuffed; Macklem was informed that if he did not wish to discuss the matter, the interview would be ended and he would be taken back to his cell. Under the totality of these circumstances, Macklem was not in custody for Miranda purposes. Even if admission of Macklem’s statements at trial was error, it was harmless as the statements were not essential to proof of the tried offenses. This opinion also considered joinder (Pen. Code, sec. 954) and found that the court had not abused its discretion in permitting joinder as the two separate attacks showed some kind of similarity of motive and planning and each case was supported by comparably strong evidence. Lastly, for the purpose of presentence custody credit, credit for time served commences on the date a defendant is booked into custody and not when he is arrested and placed in the patrol vehicle. (Pen. Code, sec. 2900.5; People v. Ravaux (2006) 142 Cal. App.4th 914, 919-921.)