so lawyers have certain duties they must abide by (such as duty to advise and duty to the client) … however there are also conflicts of interest they must be aware of (in this case it would be solicitor-client), where the lawyer knows of their clients guilt they have a few options but ultimately they must still act within the best interests of their client no matter what - check rule 20.2 of USCR. There are also some rules which allow the solicitor to come forward and disclose such confidential information.
There was actually a case about this where a man was falsely convicted of murder and he was only acquitted after the actual criminal had passed, and it was only then that those lawyers said something.