An Auckland woman made a sex tape of her ex-husband and tried to blackmail him into giving her fulltime custody of their child, a court has heard.
The woman, whose name is suppressed to protect the identity of the child, is on trial in the High Court in Auckland.
She is charged with making an intimate visual recording and blackmail.
Crown prosecutor Nick Whittington said the pair separated in 2007 and the man later remarried.
In November 2012, the woman wanted to move to Wellington with their 7-year-old daughter but the man opposed the move.
"[The woman] had an insurance policy. She had compiled a dossier of dirt that she kept on her computer," Whittington said.
The pair had continued sleeping together after the man's new marriage. The woman allegedly made a recording of them having sex and kept incriminating text messages.
The Crown alleged the sex tape was made without the man's knowledge and the woman threatened to show his new wife.
The "benefit" she aimed to achieve was custody of their child.
Whittington said police searched the woman's house and found a USB stick with the video and conversations about their liaisons from the messaging app WhatsApp on it.
Text messages sent after the pair had sex would show the man did not consent to the recording, Whittington said.
The man had seen a light on the woman's computer and was worried he had been recorded.
The woman "played dumb", Whittington said.
The parties in the case agreed to certain background facts including that the pair had sex on July 16, 2012, and a recording was made "without the explicit consent" of the man.
Whittington said the woman would probably argue consent was "implicit" in what went on.
The trial before Justice Raynor Asher is set down for three days.