Most officers are familiar with the practice of inviting suspects to the station for a voluntary interview and giving them a "Beheler admonition" ("You're not under arrest. You're free to leave anytime you want."). However, cases continue to arise where an officer with good intentions creates admissibility issues and potential civil liability problems by giving an unnecessary Miranda admonition in such cases.
In People v. Guerra (2006) ___ C4th ___ , DJDAR 2547, WL 488528, a homicide detective needlessly Mirandized a murder suspect at a voluntary stationhouse interview instead of giving a Beheler admonition, and the process backfired. The suspect said, "I want an attorney." The detective then created a Miranda issue by continuing to question, and created a voluntariness issue by threatening arrest: "If you want an attorney and don't want to talk to us, you're going to be arrested for murder and booked into jail right now."
If a person is in police custody and being subject to interrogation, they are entitled to their Miranda warnings. Without the Miranda warnings, any subsequent statement will be inadmissible in court.
A Beheler admonition is used by the police to try and show a person is not in custody. By telling a person they are "free to go" or words to that effect, they are removing the "custody" part of the Miranda requirement.
If a person acknowledges they are there voluntarily and are free to go, any subsequent statement is normally admissible. There are other factors, though. Coerced statements are inadmissible. The totality of the circumstances would need to be explored to further determine what statements, if any, are admissible.
For more about the Miranda warnings and coercive statements, see the link below: