When a witness is cross-examined, he may, in addition to the questions herein before referred to be asked any questions which tend-
- to test his veracity.
- to discover who he is and what is his position in life, or
- to shake his credit, by injuring his character, although the answer to such questions might tend directly or indirectly to criminate him or might expose or tend directly or indirectly t expose him to a penalty or forfeiture.