After leaving her baby to drown during bath-time, a mother wrapped his lifeless body in blankets and logged on to her Facebook page, a court was told.
She spent the next half hour checking out friends' pages and catching up on news on the Fiji Times website before telling her husband the baby was dead, the Crown alleges.
The 29-year-old Auckland woman, who has interim name suppression, is charged with murdering her 13-month-old son on November 8 last year.
The names of the woman's husband, her five-year-old daughter and the baby are also suppressed to protect her identity.
The woman pleaded not guilty to the charge when her trial began in the High Court at Auckland yesterday.
In her opening address, Crown prosecutor Rachel Reed said the previously safety-conscious mother had deliberately left her son, known as Baby A, to die in the bath at their New Lynn home.
"She could not cope with both of her children and saw no other way to cope with the problem than by his death."
The woman had been in an abusive relationship with the baby's father and in early 2009 had been staying at a Women's Refuge with her children. The case managers at the refuge became concerned with the woman's mental health, noting she seemed "obsessed with her husband and not able to cope with her children", Ms Reed said.
The two children were taken into the care of Child, Youth and Family, and had been returned to the woman's care only two days before Baby A's death.
On the morning of November 8, the woman had placed Baby A in the bath, filled it with water up to his chest and placed toys in the water before washing him, Ms Reed said.
Then she left the bathroom, pulling the door till it was almost shut, and prepared toast and Milo for her daughter in the kitchen, the court was told. "She deliberately let him drown in the bath because she could not cope with them both, " Ms Reed said.
It was 15 minutes before she checked on her son again, Ms Reed said. "When she eventually went back to the bathroom [Baby A] was face down in the water. She said she grabbed him out and she shook him."
The woman wrapped Baby A in towels and a blanket and left him on her bed, Ms Reed said.
Then, at 8.52am, she logged on to her laptop and opened up Facebook. "She used the internet for the next 25 minutes until the very moment her husband returned from work and she told him baby was dead."
During a later police interview, the woman said she had believed the baby would be OK if she left him alone in the bath: "I thought he would be ... just playing around with his toys that I put in the bath and he would be fine."
The woman had previously worked as a dietician for five years. The court was told she had been responsible for advising new mothers on nutritional needs for their newborns.
The woman's lawyer, John Anderson, said his client had been in a "major depressive state" at the time of Baby A's death.
"The defence case is that [Baby A's] death was an accident. An awful accident with fatal results but an accident, nonetheless.
"She was simply preoccupied with her daughter for 15 minutes and she never thought that any harm would come to [Baby A]."
The trial has been set down for three weeks before Justice Tim Brewer.