A woman accused of helping her stepbrother and alleged lover clean up after the sadistic murder of their parents has been released.

Karen Klein, 22, was set free after her lawyers in Argentina argued she had acted under pressure from her co-accused, Leandro Yamil Acosta, 25.

They said she had helped him clean up after he shot his stepfather in the head, then killed his mother with another three bullets when she returned a few hours later from taking his twin stepbrothers aged 11 to school.

He admitted the killings and also said he had eaten part of his dad’s body and had sex with the couple’s corpses. He then cut up the remains and burnt them before feeding what was left to the family’s six dogs.

The young woman’s lawyer, Monica Chirivín, said that Leandro had told her he felt “an orgasmic relief” after shooting his father and stabbing his mother, and that he had “no regrets”.

The court accepted that there was not enough evidence to charge her with the murder of her father Ricardo Ignacio Klein, 54, and his partner Miryam Esther Kowalczuk, 52, who was the mother of Leandro.

Frightened Klein said she was asleep at the family home in the neighborhood of Pilar in Buenos Aires, Argentina, when the murders took place and only agreed to help clear up because she felt that if she did not, he might kill her too.

“I did not kill. I have a clear conscience,” Klein said.

“My only mistake was not having denounced and I did not because [Acosta] was going to kill me and my brothers.”

Some body parts were found outside on the terrace in paint pots and other parts are believed to have been taken to a local waste site.

Police also recovered $10,000 cash they believed belonged to the victims, as well as a 9mm revolver, a rifle, a machete, three hatchets, two shovels and a pitchfork.

The principal hypothesis of the prosecutor Marcelo Vaiani was that the crime was motivated by the hate Acosta felt for his parents and he did it so he could be left with the property and money.

Acosta claimed he was abused by his parents when he was younger and they were also abusing his 12-year-old step twins who he wanted to protect.

Click for more from News.com.au.