The jury that found a Christchurch woman guilty of murdering her husband was unaware she is already serving a prison sentence for another crime.
Helen Milner, 50, was convicted on Thursday in the High Court in Christchurch of killing her husband Philip Nisbet by spiking his food with a drug to which he was allergic.
It emerged on Thursday she was in prison throughout the trial for trying to pervert the course of justice, at the expense of her own son.
Milner had complained to the police that her son Adam Kearns, who was 18 at the time, had been sending threatening texts to her phone, in breach of a restraining order.
He spent 16 days in custody before the police discovered the texts were sent by Milner herself.
She was sentenced to prison for two years and eight months, and was later denied parole.
She had also been convicted of fraud worth $29,000.
Milner, who has been dubbed the Black Widow, will be sentenced in February for the murder of her husband.
Milner's son Adam Kearns now plans to sue her. Lawyer Kerry Cook said papers will be filed on Friday in a claim for $60,000 as damages for being framed.