Table schema:
CREATE TABLE table_name_96 (semi_final_dual_television_commentator VARCHAR, grand_final_television_commentator VARCHAR, spokesperson VARCHAR)

Question: What is the semi-final dual television commentator status of the year with Pierre Tchernia as the grand final television commentator and an unknown spokesperson?
SQL: SELECT semi_final_dual_television_commentator FROM table_name_96 WHERE grand_final_television_commentator = "pierre tchernia" AND spokesperson = "unknown"