The mother of a baby whose murderer was sentenced to at least 13-and-a-half years in prison has described her former partner as a monster who ripped her whole world out from under her.
Matthew Ellery, 23, was sentenced to life in prison on Tuesday for killing Serenity Scott, who died two days after being hurt in her home in the Waikato town of Ngaruawahia.
Ellery was not Serenity's father, but was her mother Chelsea Scott's partner.
During sentencing, the court heard Ellery was angry at the six-month-old's crying and held her upside down and threw her on the floor and smothered her until she stopped crying.
Ms Scott told the court: "My whole world got ripped out from under me. One day I'm a happy mum and the next confusion sets in as I see my once wriggly, jolly baby girl lying still and unresponsive in her cot. Then to be told at the hospital she's not going to make it. That's something I wouldn't wish on my worst enemy."
Addressing Ellery she said: "Your behaviour and lying has had a huge effect on me and my relationships with my kids. For me, I can only see you as a monster that ruined my life.
"I will never be the same again and my kids will never get to know their mum in a real sense."
Justice Toogood said he agreed with the Crown a minimum period of 17 years in prison should be the starting point for setting the non-parole period.
"Serenity was an extremely vulnerable victim. An innocent and defenceless six-month old infant who was entirely dependent on you and the other adults in the house to care for and look after her."
He took into account Ellery's age at the time of offending, his psychological issues, remorse and guilty plea when deciding the final non-parole period.
He sentenced Ellery to life in prison with a minimum non-parole period of 13-and-a-half years.
Undercover officers got confession
For months after the killing Ellery denied he was responsible and police used undercover officers to get him to confess which he finally did last January, nine months after Serenity's death.
He was arrested but didn't plead guilty until August this year.
His lawyer Bruce Hesketh told Checkpoint how the police got Ellery to admit what he'd done.
Too little, says trust
Sensible Sentencing Trust spokesperson Ruth Money says the sentence was discounted too much.
"A six-month old baby is the most vulnerable baby bad victim that you will get. He was malicious in the way that he covered it up; denied it; and blamed a member of the victim's family. It's just outrageous. It shouldn't be anything less than 17 years."
Police said afterwards the case showed the need for parents, caregivers and guardians to protect, care for and love their children.
Waikato Detective Senior Sergeant Mark Greene says the thoughts of the police are with Serenity's immediate and extended family, who suffered greatly from the callous act that led to her death.
He also thanked those in Ngaruawahia who made it clear that child abuse is not accepted or tolerated.