A California judge has reduced a child rapist's mandatory 25-year sentence down to only 10 - saying anything longer would be 'cruel and unusual punishment'.

Superior Court Judge M. Marc Kelly told an Orange County jury that 20-year-old Kevin Jonas Rojano-Nieto 'did not intend to harm' the three-year-old girl he raped at his family home in June.

The judge said that he was sure that although Rojano-Nieto sodomized the girl and covered her mouth so she couldn't scream out, 'there was no violence or callous disregard for the victim's well-being'.

Controversial: Superior Court Judge M. Marc Kelly (seen here with a colleague in 2010) has handed a 10-year sentence to a 20-year-old child rapist. The mandatory sentence should be 25-years to life

Judge Kelly also said Rojano-Nieto, 'inexplicably became sexually aroused but did not appear to consciously intend to harm the victim.'

Prosecutor have said they will appeal the controversial decision and will be pushing for the minimum sentence of 25-years to life to be reinstated.

Rojano-Nieto was found guilty on December 3 of raping the girl who wandered into a garage where he was playing video games.

According to the court news service, Rojano-Nieto said he became aroused by the girl and pulled her pants down to rape her during the sickening attack.

While this was going on, he could apparently hear her mother calling out for her, so covered her mouth so she couldn't scream back.

The girl told her mother after the assault that she was in pain and her mother called the police who found injuries consistent with rape.

Rapist: Kevin Jonas Rojano-Nieto has been sentenced to 10-years behind bars for the rape of a 3-year-old girl

“Although serious and despicable, this does not compare to a situation where a pedophilic child predator preys on an innocent child,” Superior Court Judge M. Marc Kelly said according to KTLA.

Deputy District Attorney Whitney Bokosky said she disagrees and will appeal.