When did Natalia start being on the show? Like her very first episode doesn't matter if she was a REAL Đội điều tra hiện trường hoặc not.

From the imdb page it shows her first episode was on the 19 September 2005 which was called 'Fromthe Grave'. It was Season 4 episode 1

hope this answered your question

season four, first episode

it was 4.01 from the grave.