The killers of abused Taupō boy Moko Rangitoheriri have had their case rejected by the Court of Appeal.
The three-year-old was killed by his caregivers Tania Shailer and David Haerewa, who beat and kicked Moko to death in 2015.
The pair were sentenced last year to 17 years in jail for manslaughter, with a minimum non-parole period of nine years.
The case sparked nationwide outrage and a petition to Parliament calling for an end to plea bargaining.
Justice Kos said in the Court of Appeal decision that "the duration, cruelty and physical depravity" of the offending by two adults acting together against a defenceless three-year-old "placed it within the most serious of cases for which the penalty of life imprisonment is prescribed".
The sentences were "entirely within range and not manifestly excessive".
"Ms Shailer and Mr Haerewa can count themselves fortunate that they were not sentenced to life imprisonment," Justice Kos said.