New evidence means the three Russian sisters who killed their father could be spared jail, finding that they were suffering from post-traumatic stress disorder at the time of the crime.
Fresh psychiatric evaluation has improved the chances none of the siblings will go to jail for stabbing alleged mafia boss Mikhail Khachaturyan, 57, who they claim sexually abused them.
Using his own hunting knife as a weapon, Krestina and Angelina Khachaturyan, then 19 and 18, and younger sister Maria, 17, have admitted to killing their father after claiming they had faced 'years of abuse'.
The two elder sister are facing murder charges, while younger sister Maria was found mentally unfit to stand trial for murder.
However, because of latest evaluation demanded by the court, the new evidence could become key in their upcoming trial.
Psychiatric experts at Russia's respected Serbsky Centre say the sisters were suffering from PTSD at the time of the crime.
Lawyer Maria Davtyan said: "The experts found that since 2014 each of the girls has suffered from abuse syndrome and post-traumatic stress disorder.
"All of these conditions in his daughters have a direct causal relationship from Khachaturian's actions."
When the sisters killed Khachaturian as he slept, they were in an 'unstable' psychological state and felt 'hopeless', fearing for their lives, Davtyan claims.
Other family members have accused the sisters of lying about their father's sexual abuse.
Another lawyer Alexei Liptser representing the sisters said: "Khachaturyan's relatives claim that the sisters invented everything because they suffer from a sexual disorder.
"But according to the experts, no such disorder was found in them."
Younger sister Maria, if convicted, will face time in a psychiatric hospital rather than jail after being judged temporarily insane at the moment her father was killed.
The elder sisters are more likely to be seen by the court as acting in self-defence in Russian law.
The investigation earlier found they faced 'physical and mental suffering... over a long period of time'.
Evidence showed the father threatened one of his 'terrified' daughters: "You will take the place of your mother."
Almost one million have signed petitions calling for the sisters to go free.