A Michigan judge has spared a 13-year-old murderer a possible life sentence, ordering him to be held in juvenile detention until he is 21, when he will be released.

Nathaniel Abraham was convicted of an adult charge of second-degree murder last year, but Oakland County Family Court Judge Eugene Moore called the law under which he was charged "fundamentally flawed".

"While there is no guarantee Nathaniel will be rehabilitated at 21, it is clear 10 years is enough to accomplish this goal," Judge Moore said.

Abraham was convicted on 29 October of shooting dead Ronnie Greene, 18, with a .22-calibre rifle in the northern-Detroit suburb of Pontiac in 1997 - he was 11 years old at the time of the crime.

Prosecutors had requested a so-called blended sentence, under which Abraham would have been held in juvenile custody until age 21, then considered for adult prison if he had not been rehabilitated.

But Judge Moore told the boy society had failed him and that he must be allowed the chance to rehabilitate himself.

"We have eight years. Together we and Nathaniel can make the difference in his life," he said.

'Blended' sentence

The case gained national and international attention when Abraham became the first youth to be charged with first-degree murder and tried as an adult under a 1997 Michigan law that allows adult prosecutions of children of any age in certain serious cases.

At his trial in October, he was acquitted of first-degree murder, which could have meant life in prison without parole.

The prosecution put forward testimony that Abraham should be placed in juvenile custody with a decision made later on a possible adult prison sentence.

Susan Peters of the Department of Corrections testified for the prosecution that, based on the seriousness of Abraham's offence, decision should be deferred on adult imprisonment until he was older.

"[It is] my belief that this offence was too serious to take a chance that he might not be rehabilitated in the juvenile system, then at age 21 leave this court without any options," Ms Peters said.

On Wednesday, Oakland County Prosecutor Lisa Halushka said the blended sentence meant the boy need not serve any time in adult prison, if he was able to rehabilitate himself in juvenile custody.

"It's never been our position that we were going to lock Nate up and throw away the key," she said.

Mercy pleas

Earlier, members of the local chapter of the National Association for the Advancement of Coloured People protested against the possibility of an adult sentence outside the court.

"I hope the judge will show mercy and sentence him as a child," said H Bill Mazey, one of the chapter's executive committee.

Tests carried out on Abraham in 1994 revealed that he was emotionally retarded.

Amnesty International chose the boy's frightened face to illustrate the cover of a 1998 report condemning the US justice system as being too harsh on juveniles.