The brother of former EastEnders actress Gemma McCluskie endured months of abuse from her, culminating in her threatening him with a knife on the day he killed her, he is expected to tell a jury.
Tony McCluskie, 35, will describe how his sister's behaviour had become volatile and abusive towards him, and she pulled a knife on him on March 1 2012 - the day of her death.
McCluskie admits killing 29-year-old Miss McCluskie, but denies murder. He claims he has no memory of killing and dismembering his sister, and the Old Bailey heard that he will adopt defences of lack of intent and loss of control.
He will give evidence this afternoon.
Miss McCluskie's torso was found in a suitcase in the Regent's Canal in east London, followed by her limbs in plastic bags.
Her head was found six months later and she was officially identified by dental records.
The prosecution said pot-smoking McCluskie bludgeoned his sister to death in the flat they shared after a row about an overflowing sink.
Opening the defence case, McCluskie's barrister, Jeremy Dein QC, told the jury: "The first line of defence raised for your consideration is lack of intent.
"Albeit that Mr McCluskie will say that he cannot recall what happened, he will maintain that he did not intend or, given that he cannot recall what he actually did, cannot have intended either to kill Gemma McCluskie or to cause her at least really serious bodily harm.
"The second line of defence, loss of control. Even if, contrary to our submissions, you feel sure that Mr McCluskie did intend either to kill Gemma McCluskie or to cause her really serious bodily harm, the defence of loss of control is raised.
"In this case then, the background of months of Gemma behaving frequently, not always, Mr McCluskie will say, in a volatile and abusive way towards the defendant, that trigger, according to the evidence he will give, was the production of a knife and the making of threats on March 1."
Miss McCluskie played Kerry Skinner, the niece of Ethel Skinner, in the BBC soap in 2001.Suggest a correction