What is the current state of the law on coercive interrogation by a police detective?

"The business of police detectives is investigation, and they may elicit incriminating information from a suspect by any legal means. '[A]lthough adversarial balance, or rough equality, may be the norm that dictates trial procedures, it has never been the norm that dictates the rules of investigation and the gathering of proof.' [Citation.] 'The courts have prohibited only those psychological ploys which, under all the circumstances, are so coercive that they tend to produce a statement that is both involuntary and unreliable.'" (People v. Jones (1998) 17 Cal.4th 279, 297-298.)