A divorced man now on trial for murder swore he'd pretend to be insane if he ever got in trouble with the law, his former flatmate claims.
Manchao Li, 65, denies murdering Zhimin Yang in West Auckland last year and breaching a protection order.
Li's former flatmate Chloe Joyce told the High Court at Auckland the murder-accused asked her to help him bargain for a knife shortly before the alleged murder in Massey.
"It just kind of freaked me out in a way," Joyce said.
Prosecutors claim Li was obsessed with revenge after a property dispute and killed his ex-wife, 56, in a stabbing frenzy on July 29 last year.
On Thursday, Joyce told the court Li mostly talked about his past life in China, and obsessively complained about his ex-wife, who was also known as Jennifer.
"He always referred to her as 'bitch' or 'the woman'. He would say how she tricked him into signing a marriage certificate."
Joyce said Li described a shambolic marriage where the couple slept apart and he claimed his ex-wife stole thousands of dollars from him years earlier.
Li and Yang divorced in 2009.
The former flatmate said Li exhibited signs of depression.
"But depression doesn't make you go kill someone," Joyce added.
"He's very isolated," she told defence counsel Sam Wimsett. "He would just be in his own little bubble and his own little world."
Joyce claimed she overheard a conversation Li had with her partner at the West Harbour house.
"I heard Li saying that if he ever gets caught doing anything ... He's just going to say he's insane."
She said that conversation happened last July.
"It's really mind-boggling, you know."
Another witness, Yang's former Massey Library manager Joanne Crummer, said Yang warned library staff about Li in 2014.
Crummer said Li the following year faxed her about 20 pages of highly personal information.
Crummer said the incident was bizarre and inappropriate, and she gave the documents to Yang.
She said once when Li turned up at the library, Yang was terrified and refused to leave the library through the front, instead getting a friend to pick her up from the back door.
Crummer said she trespassed Li from the library once for allegedly harassing Yang.
"He was sweating and he asked me what he had done wrong."
The jury trial earlier this week heard members of the public rushed to help Yang after Li allegedly stabbed her 12 times with a hunting knife.
He allegedly had been following her and then attacked her from behind while she was waiting for a bus on Westgate Drive.
The trial continues.
Domestic violence - do you need help?
If you're in danger now:
• Phone the police on 111 or ask neighbours of friends to ring for you.
• Run outside and head for where there are other people.
• Scream for help so that your neighbours can hear you.
• Take the children with you.
• Don't stop to get anything else.
• If you are being abused, remember it's not your fault. Violence is never okay
Where to go for help or more information:
• Shine, free national helpline 9am- 11pm every day - 0508 744 633 www.2shine.org.nz
• Women's Refuge: Free national crisis line operates 24/7 - 0800 refuge or 0800 733 843 www.womensrefuge.org.nz
• Shakti: Providing specialist cultural services for African, Asian and middle eastern women and their children. Crisis line 24/7 0800 742 584
• It's Not Ok: Information line 0800 456 450 www.areyouok.org.nz