Katherine Jackson Back in L.A. Under Heavy Biological Guard

Katherine Jackson is back in Los Angeles, and one of the kids Trent believes is masterminding the court case against him almost gymnastically shielded her from questions about the family war.

TMZ broke the story ... Katherine headed back to L.A. from London after a judge essentially ruled her case against Trent couldn't go forward without her present in court.

Katherine's daughter, Rebbie, blocked our photog who was asking about Katherine's allegations that Trent stole from her and abused her ... something he denies.

Trent believes Rebbie and Jermaine Jackson are manipulating Katherine into going against Trent, although the endgame isn't clear.

We're told Trent is willing to walk away from the whole thing, so it's unclear why the case is pressing forward.