Is contact between a juror and a witness improper?

We shall consider the contact between the juror and the witness first. " ' "[N]ot every incident involving a juror's conduct requires or warrants further investigation. 'The decision whether to investigate the possibility of juror bias, incompetence, or misconductlike the ultimate decision to retain or discharge a jurorrests within the sound discretion of the trial court.' " [Citations.] " '[A] hearing is required only where the court possesses information which, if proven to be true, would constitute "good cause" to doubt a juror's ability to perform his duties and would justify his removal from the case.' " [Citation.]' [Citation.]" (People v. Cowan (2010) 50 Cal.4th 401, 506.) "A juror's unauthorized contact with a witness is improper. [Citations.] However, contact between a juror and a witness . . . may be nonprejudicial if the contact was 'de minimis' [citation] if there is no showing that the contact related to the trial [citations]." (Id. at p. 507.)