The defendant’s petition for certification for appeal from the Appellate Court, 20 Conn. App. 115, is granted, limited to the following issues:

“1. May the state, in a criminal prosecution, require a defense witness to invoke the privilege against self-incrimination in open court, and may it use such invocation and subsequent waiver as a basis for impeaching the witness and for adverse comment in its summation?

“2. If the trial court’s ruling to permit such conduct was erroneous, was the Appellate Court correct in concluding that the error was harmless?”