Patricia Arquette -- 'Boyhood' Plays Out In Ex's Bitter Divorce

"Boyhood" star Patricia Arquette and her son are being dragged into her ex's ugly divorce trial ... and it sounds like they're solidly on his side.

Back in the late '80s, Arquette gave birth to Enzo -- now 26 -- with then boyfriend, musician Paul Rossi. But similar to the movie ... he split when Enzo was just a month old and remained a present father.

Fast forward to the divorce ... estranged wife Kerry-Ann Johnston-Rossi claims in court docs Rossi is verbally abusive, threatening, and she lives in constant fear. Rossi has fired back that she's a liar, and that's why he's calling Patricia and Enzo to testify on his behalf ... as character witnesses.

The docs say Patricia/Enzo will testify about Rossi's "parenting abilities, lack of any violent or angry tendencies." And according to the docs, Patricia may have harsh words for Kerry-Ann ... regarding her "parenting abilities, her anger and/or violent tendencies."

The trial is set for March. Nothing like having a possible Oscar winner in your corner.