Any competent witness in a cause shall not be excused from answering a question relevant to the matter in issue, on the ground merely that the answer to such question may establish, or tend to establish, that such witness owes a debt, or is otherwise subject to a civil suit; but this provision shall not be construed to require a witness to give any answer which will have a tendency to accuse himself of any crime or misdemeanor, or to expose him to any penalty or forfeiture, nor in any respect to vary or alter any other rule respecting the examination of witnesses.