A Metra passenger launched a profanity-laced tirade at her son Saturday, then beat a judge on the train who showed support for the boy, according to Cook County prosecutors.

Elizabth Pope, 33, was on the upper level of Union Pacific North train No. 301, set to leave Ogilvie Transportation Center at 12:35 a.m., court records show. Pope was taking the nearly two-hour ride to her home in Kenosha, Wisconsin home, with her 14-year-old son.

As the train was leaving, Pope began berating her son, prosecutors said. “You are a f—— idiot,” she told him.

A 57-year-old Lake County judge on the lower level of the train on the way home from a concert made eye contact with the boy and told him, “You are not an idiot,” prosecutors said.

Pope, who smelled of alcohol, told the woman to stop talking to her son, then walked down the stairs and started punching her, prosecutors said. She also hit the judge in the face with a cellphone then threw the phone down the aisle.

The judge pleaded with another passenger to get a conductor as she started bleeding from the punches, prosecutors said. When the conductor reached the third train car, he found Pope back up on the upper level sitting with her son. She was taken off the train and arrested in Ogilvie.

Paramedics took the judge to Rush University Medical Center, where she was treated for bruising and swelling in the face, court records show. She needed five stitches to her upper lip.

Pope was charged with aggravated battery in a public place. She has two previous battery convictions and another pending battery case, prosecutors said.

“You beat a woman because she had the audacity to show support for your son,” Cook County Judge Michael R. Clancy told Pope in court Sunday as he set her bail at $70,000. Clancy also ordered Pope to be placed on electronic home monitoring if she posts bond.

Pope is next scheduled to appear in court on Friday.