John 12:42-43

Even though most of the Jews rejected Jesus, some believed on Him (cf. John 1:10-13). Even some of the rulers did, though the content of their faith doubtless varied. Nicodemus and Joseph of Arimathea seem to have been such people (cf. John 7:50-52; John 19:38-39). Most of them did not admit that they believed in Him, however, because of fear of exclusion from synagogue worship (cf. John 9:22).

Public confession of faith in Jesus is the normal expression of belief in Him (Romans 10:9-10). However public confession is not a condition for salvation. Obviously mutes and other people can believe but for one reason or another may not be able to confess their faith publicly with their mouths.