An Adelaide couple who kidnapped and tortured their babysitter by locking her in a cupboard and forcing her to eat dog food have been jailed for what the judge described as a "mindless, cruel and sadistic" crime.

Joshua Anthony Gent, 29, and Keira Jane Baker, 28, accused their babysitter of reporting their friend to police over a car theft, telling the young woman she was a "dog" who needed to be taught a lesson.

The District Court heard the couple forced her into the boot of their car and drove her to the house of their friends, Patrick James Breen, 25, and Stacey Gaffney, 23.

During the horrifying 18-hour ordeal, she was subjected to beatings, abuse and deprivation, all while Gaffney's two young children were in the home.

The court heard she was told to bark like a dog, choked and dragged around the house with a leash, and had squeaky toys shoved into her mouth while she was assaulted.

She was forced to eat dog food while the two couples laughed and filmed her torture.

The young woman was also burnt with an ice pipe, forced to inhale the drug, while threats were also made that she would have to drink bleach.

Judge Jack Costello said they threatened to sell her to a man who she would be forced to have sex with, telling her that if she refused, "she wouldn't last".

"She truly believed that you were going to kill her," he said.

Judge Costello said Baker punched the young woman repeatedly in the face, causing her to fall to the floor, before threatening to cut her fingers off with various tools.

"You, Baker, then hit her really hard across her fingers," he said.

"You, Gent, yelled in her face calling her a dog and kicked her in the stomach."

Judge Costello said the victim was locked in a closet for some time before Gent dragged her into the bedroom by her hair, where she was punched and kicked and told not to bleed on the carpet.

"So distraught was she by this time that she simply urinated all over herself," Judge Costello said.

'Depravity simply beggars belief'

Judge Costello described the ordeal as an act of "mindless, cruel and sadistic violence" which would psychologically scar the young woman for the rest of her life.

"She suffers from an overwhelming fear. Quite simply, she has been robbed of her ability to enjoy life," he said.

"Any prospect of her resuming something approaching a normal life even in the medium to long term remains quite unclear.

"Such wanton violence and depravity simply beggars belief. That some of you could treat a fellow human being this way strikes at what underpins the essence of a civil society, namely our respect and dignity of our fellow human beings."

All four pleaded guilty to unlawful detention of a person, with all but Gaffney also pleading guilty to aggravated counts of causing serious harm.

Baker and Gent also confessed to making threats to kill.

Gent, who the court heard was the instigator of the torture, was sentenced to 15 years and seven months in jail, with a non-parole period of nine years and two months.

His partner Baker sobbed in the dock as she was jailed for just over 10 and a half years with a non-parole period of six years and two months.

Breen, who conducted internet searches on "how to terrify someone who has been kidnapped", was sentenced to six years and seven months' jail with a non-parole period of just under four years.

Judge Costello suspended Gaffney's two-year and two-month jail sentence on a $500 good behaviour bond.

He said, Gaffney, who had lost her job as an enrolled nurse as a result of the offending, had no prior criminal history and had played a more passive role in the ordeal.