Is a promise made by a police officer or person in authority of leniency or advantage to the accused sufficient to invalidate the confession?

"The cases in this court are clear from the earliest time that any promise made by an officer or person in authority, express or implied, of leniency or advantage to the accused, if it is a motivating cause of the confession, is sufficient to invalidate the confession and to make it involuntary and inadmissible as a matter of law." (People v. Brommel (1961) 56 Cal.2d 629, 632, 15 Cal.Rptr. 909, 364 P.2d 845.) The comments made to appellant by the police prior to the first and third interrogations clearly implied an advantage to the appellant if he talked since it was indicated that, if he cooperated, the police would help him. The use of phrases such as "we would see what we could do to help [you]" and "maybe we can help you with this part of the treatment or you know what might happen" (emphasis added) carry the clear implication that appellant could expect more lenient treatment if he [31 Cal.3d 839] were to confess than if he persisted in his denials. The language used in this case is quite similar to that held improper in the case of People v. Gonzales (1902) 136 Cal. 666, 668, 69 P. 487, where the sheriff said he "would do whatever he could" for the defendant, if the defendant repudiated his denial and admitted guilt. ⁸