Murder accused Malcolm Webster's sister-in-law has told a court that his New Zealand wife wondered if he was spiking her food and drink.
Webster, 52, of Surrey, in England, is on trial in Glasgow's High Court, charged with twice attempting to kill Aucklander Felicity Drumm in New Zealand in 1999.
In one of the charges he is accused of trying to kill her by administering Clonazepam and other controlled drugs, while in the other prosecutors say he tried to kill her in a car crash on the Auckland motorway on February 12, 1999.
Webster has also denied murdering his first wife Claire Webster by drugging her, crashing his car on a Scottish road and setting it on fire in May 1994.
His sister-in-law, Janine Webster, told the High Court she did not offer Ms Drumm any advice, and added: "Perhaps I was like the proverbial ostrich."
Mrs Webster, 49, who is married to Mr Webster's older brother Ian, said Ms Drumm was worried because she was sleeping for lengthy periods, the BBC reported.
The witness told prosecutor Derek Ogg QC that the conversation happening before Ms Drumm and Mr Webster went to New Zealand in December 1998.
Mr Ogg asked: "What advice did you give her?"
She replied: "I didn't and I regret that."
Mr Ogg: "Did she express to you what she thought might have been happening?"
Mrs Webster: "She wondered whether Malcolm was spiking her food and drink."
Mr Ogg: "That's extraordinary."
Mrs Webster: "It is extreme."
Mrs Webster said she did not tell Ms Drumm to go to her doctor to get checked out, and added: "With hindsight I should have."
Her husband told the court his brother had received a payout of £200,000 from insurance polices after his first wife's death.
The court was told that after leaving New Zealand - and Ms Drumm and their son - Webster eventually moved to Oban in Scotland and began a relationship with Simone Banarjee.
Mr Webster said that he was uncomfortable speaking to her because he knew his brother had not told Ms Banarjee that he still had a wife and child in New Zealand.
Webster has denied the two charges of trying to murder Ms Drumm, the murder of his first wife and of forming a fraudulent scheme to cash in on Ms Drumm's life insurance policies and inducing her to make a will leaving her estate to him.
He has also denied forming a fraudulent scheme between 2004 and 2008 to enter into a bigamous marriage with Ms Banarjee to get access to her estate.
The trial before Judge Lord Bannatyne continues.