Lauren Anne Dickason was charged with murdering her daughters Liane, aged six, and twins Maya and Karla, aged two.
Dickason, who is on trial in the High Court in Christchurch, New Zealand, has admitted to killing her children but denies it was murder.
Her defence claims she is not guilty by reason of insanity.
“I did the twins first… The first one was being really, really, really horrible to me lately,” the mum explained, referring to Karla.
“She has been biting me and hitting me and scratching me and throwing tantrums 24 hours a day – and I just don’t know how to manage that. That is why I did her first.”
She explained that the children were jumping on couches and not listening to her.
So she went to the garage, spotted some cable ties and thought, “That could possibly work”.
In the interview, Dickason admitted she “had been thinking about it for sure,” and put the three sisters in a room before using the cable ties on them.
That attempt was unsuccessful, however, so she suffocated them.
Detectives then heard that Dickason tucked each child into their beds, pulling the blankets over their heads fully aware that they were dead.
In the interview, Dickason admitted she “had been thinking about it for sure,” and put the three sisters in a room before using the cable ties on them.
That attempt was unsuccessful, however, so she suffocated them.
Dickason explained that in the lead-up to the alleged triple murder, she had been getting only two hours of sleep a night, was losing many kilos due to stress and had not felt normal for around nine or 10 weeks before.
Earlier in the trial, the jury heard Dickason had carried out several searches regarding how to overdose children and what the lethal or fatal qualities of specific drugs were.
Last week, Crown Prosecutor Andrew McRae alleged Dickason was an angry and frustrated woman, who resented her daughters for standing in the way of her relationship with her husband.
Mr McRae alleged the mother was fully aware of her actions and labelled the killings as methodical, purposeful and perhaps clinical.
The defence, however, argued that Dickason was “very unwell” and didn’t recognise how unwell she was until it was “too late”.
The trial will resume on Wednesday and is expected to run for at least another two weeks.
Experts are also expected to speak on whether they believe the mother was insane.