Mary Cosby was interviewed by police weeks before her son Robert Cosby Jr.’s death and was grilled about her son’s alleged domestic violence … TMZ has learned.

Per a Salt Lake City Police report, Robert’s then-wife, Alexiana Smokoff, called law enforcement on November 23, 2025.

Cops say Alexiana told them Robert was behind bars at the time, but she wanted to report an alleged domestic violence incident that she says occurred in May 2024. She claimed Robert got upset with her after she flushed his drugs down the toilet “because she was tired of his drug use.”

She told cops Robert “grabbed her by the throat with his hand and strangled her.” She also accused him of spitting on her during the incident … but she told cops she lost consciousness and did not remember everything.

Cops say the Bravo star denied her son was a violent person and noted she did not raise him that way. She also denied seeing any injuries … except for one time he and another party jumped off a balcony while high.

Police say they also spoke to Robert when he was locked up … they say he admitted he was using fentanyl at the time and did not remember everything from the 2024 fight.

Robert told police that he did tell his mom about him being physical with his wife. He told police he thought he was in a “psychosis” for a bit as he was “acting erratic and irrational” and not really acting like himself.

Alexiana filed for divorce after the incident … and the divorce was finalized while he was in jail.