Jakarta. A Jakarta judge on Monday found a 15-year-old girl guilty of becoming complicit in the brutal attack of a teenage boy by Mario Dandy Satriyo and sentenced her to three and a half years in juvenile prison.

The attack on Feb.19 left the victim David Ozora in a coma for weeks after he was punched and kicked in the head by Mario.

The hearing at the South Jakarta District Court was open to the public although the number of visitors is limited to 20.

"We pronounce that juvenile defendant Agnes Gracia Haryanto has been convincingly proven guilty of participating in a pre-planned assault," Judge Sri Wahyuni Batubara said as she read out the verdict.

She ordered the defendant to serve her term at the Juvenile Correctional Institution.

The lone judge considered the victim's condition which kept him in the hospital with serious brain damage as the aggravating factor for the sentence.

But Judge Sri also took into account the defendant's very young age and her ailing parents as the mitigating factors. Prosecutors earlier recommended a prison sentence of four years.

Mario, the prime suspect in the case, is accused of assault and battery that carries a prison sentence of up to 12 years. His trial is expected to begin at the end of this month.

He is the son of high-ranking taxman Rafael Alum Sembodo, who became a corruption suspect and was fired by the Finance Ministry last month following a public inquiry after the video of the attack was posted on the internet.

The anti-money laundering agency alleged suspicious transactions worth hundreds of billions of rupiah involving the taxman in recent years. Rafael was summoned by the Corruption Eradication Commission for undeclared assets and a further investigation revealed that he kept foreign currencies worth Rp 32 billion in safe deposit boxes.

He was detained last week.