Osvaldo Rivero
Osvaldo Rivero, 36 New Jersey Department of Corrections

A court in New Jersey has refused to grant a new trial to a man sentenced to 110 years in prison for murdering a six-year-old boy who was trying to save his 12-year-old sister from being raped.

Osvaldo Rivera was found guilty in 2014 of the murder and sexual assaults which took place in 2012.

The now 36-year-old Rivera slashed the throat of the 12-year-old twice as he sexually assaulted her on 2 September 2012, ABC6 reported.

When her six-year-old brother, Dominick Andujar, came in the room and tried to help her, Rivera also cut his throat.

The girl managed to get to a neighbour's house for help and Rivera was later found a few blocks away.

Defence attorneys attempted to get Rivera convicted on the lesser charge of manslaughter because he was intoxicated at the time.

NJ.com reported that although authorities had previously suggested Rivera had taken PCP-laced marijuana, his attorney said he was drunk.

Rivera argued that the judge should not have described other charges as "lesser" as it meant jurors went for more severe charges, rather than appropriate ones.

The argument was thrown out as Rivera's attorney at trial had asked for the degrees of charges to be told to the jurors - and the court said a defendant could not ask for one thing and then reject it when they did not get the outcome they wanted.

Along with the 110-year sentence, of which Rivera will need to serve over 82 years before being eligible for parole, he is also serving a 15-year sentence for sexually assaulting a two-year-old just weeks before the attack that left Dominick dead.