WATERVILLE — A local man who spent 20 years in prison for killing his mother after getting high and watching a pornographic movie has been charged with indecent conduct at a local adult video store.

Scott L. Thompson, 40, of 6 High St., No. 2, was detained at about 7 p.m. Sunday after walking out of the video viewing area of the First Amendment store on College Avenue wearing only sneakers and socks, Sgt. Joseph Shepherd of the Waterville Police Department said Monday.

“The clerk … asked him to go back to the viewing area and he did not, so she called us,” Shepherd said.

Thompson was on probation for breaking into another adult bookstore, Treasure Chest II, in Waterville in 2009, and for sexually groping a woman in the dressing room of a Waterville fashion store three months later. He received a 364-day jail term for the unlawful sexual touching charge and a four-year sentence, with all but one year suspended, and two years of probation for the store burglary.

Thompson had been out of jail for two months, Shepherd said.

He said the new charges against Thompson are indecent conduct, a misdemeanor, and violating probation, which could send him back to prison.

Thompson was convicted in April 1991 of murdering his mother, Edith Thompson, 59, in 1989. He was 17 at the time. He was released from prison in December 2008, having served 20 years of a 30-year sentence.

Thompson was being held without bail Monday at the Kennebec County jail in Augusta. He is scheduled to appear in court today on the indecent conduct charge, and has a Sept. 12 hearing on his probation status, according to a jail intake worker.