CREATE TABLE table_name_96 (semi_final_dual_television_commentator VARCHAR(255), grand_final_television_commentator VARCHAR(255), spokesperson VARCHAR(255))
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"