As a probation officer, Heidi Siebenaler had years of experience and training about how to tell whether one of her clients had been abusing drugs or alcohol. Yet she claimed she didn’t know her husband was using pot or there was a half-pound bag of marijuana on top of her dresser.

She should have known better, an arbitrator said in a ruling made public Tuesday. The ruling by arbitrator Jeffrey Jacobs denied a grievance filed by Siebenaler’s union fighting her firing from the job she held for 15 years. She was a probation supervisor for Dakota County Community Corrections when she was fired Feb. 3, 2012.

She had been on paid administrative leave since Nov. 2, 2011, shortly before she and her husband, Mark Siebenaler, were charged with fifth-degree drug possession. Mark Siebenaler also was charged with intent to distribute drugs after investigators found another 8-pound pot stash and alleged evidence of a grow operation in an RV outside the couple’s home in Ravenna Township in eastern Dakota County.

The case came to light when Heidi Siebenaler’s 11-year-old son took a cellphone photo of the bag of pot and sent it to his father, who notified police. The story became a media sensation, appearing in newspapers as far away as England.

According to court documents, the boy had complained to his mother about finding a glass bong in the house and reported it to his mom, who did nothing. Another time, the boy complained that his stepdad smelled like burnt marijuana. His mother at one point told him it was tanned beaver hides stored in the basement.

Drug charges against Heidi Siebenaler were quickly dismissed. Mark Siebenaler pleaded guilty to the possession charge in September 2012 and received a stay of adjudication, meaning the conviction will not be on his record if he completes three years of probation.

Heidi Siebenaler did not return phone messages left Tuesday at her home, work and cellphone numbers.

However, in an interview with the Star Tribune on Dec. 5, 2011, she said her husband’s drug use “was clear” to her.

“I didn’t support it and I didn’t want it around the house, mostly because of my job,” she said. “He knew that.”

She said then that her ex-husband was using their son as “a pawn to prove that my current husband uses marijuana.” She said her husband used the drug medically, because of a traumatic brain injury and other injuries.

“He decided he didn’t want to be on Percocet and Vicodin all day long,” Siebenaler said.

Siebenaler’s job grievance was heard by the arbitrator April 5. The county said her claims that she didn’t know about the marijuana in the house or the alleged grow operation in the RV “are simply not credible,” the ruling said.

“She either knew or should have known of the presence of this quantity of illegal drugs in her own home or … she was so blind to it that she cannot be trusted any longer.”

The county pointed out that Siebenaler sat by her husband’s side during a TV news interview in which he admitted smoking marijuana and said he “was not ashamed to say it.”

Siebenaler’s co-workers “were disappointed and badly shaken” by the news stories about the case, the county said, and “even expressed unwillingness to work with [her].”

Siebenaler’s union, the Human Service Supervisors Association, countered the county’s claims, saying the bag of marijuana in the bedroom was the only thing found in the house and it was in a sealed, opaque Menards bag. The media attention was out of her control and “was not shown to have caused any damage whatsoever to the probation office.”

The arbitrator didn’t see it that way, though. He said the media reports “badly hurt the reputation of the Dakota County probation office” and damaged Siebenaler’s relationship with law enforcement and judicial officers with whom she worked.

“There is virtually no credible way that she could not have known what was in that bag and no credible way she could have had no idea what was going on,” Jacobs wrote.