The trial of a Westbrook woman accused of allowing her boyfriend to sexually assault an underage female relative began Tuesday in Cumberland County Unified Criminal Court in Portland.

Holly Morrison, 34, of 110 Brown St., has pleaded not guilty to a six-count indictment brought against her in April on three counts of gross sexual assault, a felony punishable by up to 30 years in prison, and three misdemeanor counts of endangering the welfare of a child.

The 14-year-old victim was the first witness to testify at the trial, and was followed by other witnesses on Tuesday. Jurors were shown a video of a police interview of Morrison by Westbrook Detective Steve Crocker, in which Morrison said she knew what her boyfriend was doing and told him to stop but didn’t think to call police.

The prosecutor, Assistant District Attorney Michael Madigan, expects to call more witnesses on Wednesday when the trial before Judge Jeffrey Moskowitz continues.

Morrison appeared in court last month for a scheduled hearing on a plea agreement reached by her attorney and the prosecutor last month, but backed out of the deal at the last minute.

Madigan told the judge last month that under the terms of the plea agreement, the maximum sentence Morrison would have faced was 15 years: 10 years in prison and the remaining five years suspended during a four-year probation term.

Madigan said Morrison’s attorney, Amanda Doherty, could have argued for a lesser sentence and the ultimate decision would have been up to the judge.

Morrison has remained free on $500 bail.

She is accused of watching her boyfriend, Donald Cass, use objects to assault the girl at least three times last fall, according to court records.

Westbrook police were first alerted by school officials on Nov. 14, after the girl told friends and a counselor that she had been assaulted by Cass multiple times. The girl also told officials that Morrison insisted she get in bed naked with the couple and shower with them, according to a report by Crocker.

Cass, 59, of 57 Towle Ave. in Auburn, was arrested last year and pleaded guilty to two counts of gross sexual assault.

Cass, a former reserve police officer in Auburn, was sentenced on Feb. 24 to serve four years of an eight-year prison sentence, with the balance suspended for a four-year probation term.

Morrison told police that she met Cass at a “swingers party” and they participated together in swingers events.

Cass, who is married, told police that he visited Morrison’s home on weekends while telling his wife that he was going on hunting or fishing trips, according to court records.

As a condition of bail, Morrison was ordered to have no contact with Cass or the victim.