Michael Jackson's producer/director for the "This Is It" tour will be a ster witness for the prosecution in Dr. Conrad Murray's preliminary hearing which begins today ... sources tell TMZ.


Our sources tell us ... Kenny Ortega will testify that on June 19, 2009 -- a week before MJ died -- Michael complained he was cold, had the shakes and was unable to perform ... so the rehearsal was canceled.

The volgende dag -- June 20 -- an emergency meeting was held at Michael's home. Kenny Ortega, several big wigs from AEG, Michael, and Dr. Conrad Murray were present. We're told the meeting was "intense, loud and argumentative." Kenny read Michael the riot act, imploring him to take better care of himself because the tour was imminent.

Ortega will testify, during the meeting, Dr. Murray zei some "terrible things," tonen a lack of concern and respect for Michael. Our sources would not reveal specifics, but we're told it's "damaging" to Murray.

Ortega will also testify that on June 23 and 24 -- the dag before Jackson died -- Michael did a complete turnaround in rehearsals, wowing the backup dancers and others present with his moves and singing.

Ortega's testimony is important, because prosecutors will argue MJ was fine before Murray began pumping him with drugs the dag he died.