'Matlock' Star David Del Rio's Wife Slams Alleged Sexual Assault Victim

David Del Rio's wife, Katherine, is sticking up for her husband amid allegations he sexually assaulted his "Matlock" costar Leah Lewis ... calling Lewis "the most disturbing human being I have ever met."

Katherine posted the fiery message on an Instagram Story Thursday, showing a cropped photo of Leah from a pic of the 28-year-old actress with her mom. Katherine's post has since been deleted.

As we reported yesterday, David was escorted off the Paramount lot last week and kicked off the show as soon as the allegations against him were reported ... according to a source with direct knowledge. David has been accused of committing the unspecified act on Paramount property.

Thursday afternoon, Leah shared a pic of herself embracing her mother, writing ... "Mom is here, we're moving forward in love and strength. I'm in good hands. Thank you to everybody for any kind of support and care. Truly, we're moving forward in strength. Key word, strength. Please, let that be the take away."

That's the same photo Katherine used for her blazing response.

David's character, Billy Martinez -- one of the main ensemble of the reboot starring Kathy Bates -- will be immediately written off, CBS Studios confirmed. He's appeared in 20 episodes.

Coincidentally, the legal drama made sexual assault a theme in its third episode of the first season, in which Matlock -- played by Kathy Bates -- takes over a case after a young lawyer claims she was sexually assaulted by a superior.