ยง 4501. Self-incrimination. A competent witness shall not be excused from answering a relevant question, on the ground only that the answer may tend to establish that he owes a debt or is otherwise subject to a civil suit. This section does not require a witness to give an answer which will tend to accuse himself of a crime or to expose him to a penalty or forfeiture, nor does it vary any other rule respecting the examination of a witness.