Former NT police commissioner John McRoberts has been jailed for 12 months by a Supreme Court judge who told him he was supposed to uphold the law and not break it.
The 59-year-old was found guilty in May of attempting to pervert the course of justice.
His efforts to derail a fraud investigation into his former lover, travel agent Xana Kamitsis, to protect himself from scandal and losing his job have cost him his freedom.
Justice Dean Mildren jailed McRoberts for three years, to be suspended after one year.
When he discovered Kamitsis was the target in a major investigation into numerous Darwin travel agents found to be rorting a government pensioner concession scheme, he lied about the relationship, which included free travel, gifts, and accommodation.
He instead devised a plan to deflect and frustrate it, Justice Mildren said.
He blocked a raid on her business, that would have revealed her illegal behaviour and his affair with her through phone messages.
The pair were in relationships with other people.
Unfortunately for McRoberts, police focused on Kamitsis who was the greediest of the travel agents and was rorting the biggest amounts.
In one of many instances she illegally pocketed more than $2000 of taxpayer money by invoicing the health department $3214 for a flight to Hobart for a pensioner when the actual flight she booked cost $1111.79.
McRoberts pushed for an end to the criminal probe and for a civil remedy instead in meetings with politicians and bureaucrats, allowing the dishonest travel agents to simply pay back the money.
Unfortunately Kamitsis - ignorant about how much trouble she was in - was arrested and later jailed.
Justice Mildren told McRoberts, who rebuked his officers after Kamitsis was filmed by media while arrested, he was guilty of a gross misuse of power that "struck at the heart of justice".
Justice Mildren repeatedly said while sentencing McRoberts "without disclosing to your staff the true extent of your relationship with Ms Kamitsis and knowing it was improper for you to be involved in Operation Subatai (the investigation)" when describing his various meetings and actions in committing the crime.
"You were as police commissioner expected to uphold the law, not actively breach it," he said, adding the crime was too serious not to involve time in jail.
McRoberts had instead tried to enable Kamitsis to get away with it and damaged the reputation and morale of the police, who ultimately arrested her when the then-chief was away.
His lawyer Anthony Elliott immediately applied to appeal and for a bail application on Wednesday but McRoberts spent Monday and Tuesday night behind bars.