Prior to be taken into custody, any statements voluntarily made by a defendant are admissible in court. However, once arrested, a defendant must be read their rights (i.e. they must be given a Miranda warning) before any further questioning can continue (other than questions incidental to the booking process). If they are not read their rights but still questioned, then any of those statements are inadmissible and cannot be used against them. Finally, once a suspect is "Mirandized", they can make admissible statements if they "waive their rights" to counsel. That is, they voluntarily give permission for questioning to continue with or without the presence of their attorney.