Summoned witness with risk of self-incrimination: examine the right to refuse and statement necessity.
Anyone summoned as a witness is in principle subject to the duty to tell the truth. If a truthful statement would expose you or a relative to the risk of criminal prosecution, a right to refuse to give evidence comes into consideration. Section 290 StGB also provides a ground excluding punishment for statement necessity.
From a legal perspective it should be clarified before the examination whether a right to refuse exists and how to handle it. A false statement is never the right way; silence or refusal are the legally safe alternatives.