CREEK COUNTY, Oklahoma - The 21-year-old daughter of former Tulsa police officer Shannon Kepler was arrested Wednesday and booked into the Creek County Jail on two counts of drug possession. 

Lisa Grace Kepler, who was a key witness in her father's two previous murder trials, was arrested on complaints of marijuana possession and possession of drug paraphernalia, according to the Creek County Sheriff's Office. She turned 21 on the day she was arrested.

A law enforcement source tells News On 6 Lisa Kepler was a passenger in a car Mannford Police pulled over for speeding on Highway 51 around 1:30 a.m. Wednesday, June 28. The male driver had a suspended license, the source states.

During the traffic stop, the source said Lisa Kepler admitted there might be something in the car, and a K9 search turned up a baggie with pot in the spare tire compartment, two pipes used to smoke marijuana and a small yellow pill.

News On 6 was told Lisa Kepler admitted the stuff belonged to both her and the driver and said they had smoked pot a few hours before driving.

Kepler's father, Shannon Kepler, is currently on trial for the third time after the first two trials ended with hung juries. Shannon Kepler is charged with the murder of Lisa's boyfriend, Jeremey Lake, who was shot and killed in 2014. 

Lisa Kepler met Lake at a homeless shelter and was walking with him August 5th, 2014, when her father pulled up in an SUV. He fired shots from the vehicle, hitting Lake twice. 

Shannon Kepler admits to firing the shots but claims it was in self defense.