TMZ has learned the L.A. County Sheriff's Department wants to interview the 12-year-old son of Oksana Grigorieva in connection with the Mel Gibson investigation, and they believe the boy has critical information about his mom's volatile relationship with Mel.
Sources tell us Alexander Dalton saw many of the blowups between Mel and his mom, both before and after the explosive January 6 showdown. Alexander -- whose dad is actor Timothy Dalton -- lived with Mel and Oksana while they were together, and is considered "a very important percipient witness" to Sheriff's investigators.
Based on the information we know, Alexander did not witness when Mel allegedly struck Oksana, but he may have been in the vicinity, heard the argument and saw the aftermath.
And we're told Alexander -- who is sometimes called Sacha (Russian for Alexander) -- is also a critical witness in the couple's custody battle.
Sources tell us Oksana will not try and prevent Sheriff's investigators from interviewing her son.