The Supreme Court on Monday refused to extend the detention of the juvenile convicted in the December 2012 gang-rape of a 23-year-old paramedical student.

"We share your concern but our hands are tied by the existing law. There has to be clear legislative sanction to extend the detention period beyond 3 years. Under the present law, detention cannot be extended beyond three years," the SC said.

The juvenile convict, who is now 20, completed his three-year term at a correctional facility in Delhi on Sunday, 20 December, 2015.

The Delhi Commission of Women (DCW) chief, Swati Maliwal, had on Saturday night filed a plea with the apex court challenging the release of the juvenile convict until his mental reformation is ascertained. 

"The government of India in its stand submitted that there is no material to establish that the mental state of the respondent has been reformed. His behaviour and attitude in the special home confirmed by government agencies is that the respondent continues to have a criminal/perverse bent of mind which poses a serious threat to women," the DCW wrote in its petition.

"Thus, releasing the said respondent without even calling for an assessment of his mental state may be extremely dangerous to the society," the petition added.

Advocates Guru Krishnakumar and Devadatta Kamat, representing the DCW, told the apex court that the Intelligence Bureau had warned that a convict in Delhi High Court blast had radicalised the juvenile convict. The advocates said that IB had warned that the juvenile may repeat crimes, The Times of India reported.

The convict, whose identity has been kept under wraps for his safety, was released amid protests by victim Jyoti Singh's parents and several others in the national capital. He has been shifted to an NGO at an undisclosed location. 

The protesters also reportedly demanded death for the juvenile who was found to be the most brutal of the six convicts in the gang-rape case. 

Jyoti Singh was earlier referred to as "Nirbhaya", a name given by a newspaper. She was brutally gang-raped and assaulted with an iron rod on a private moving bus by six men, including the juvenile convict, on 16 December, 2012.

She had suffered severe injuries in her abdomen and intestines due to the brutal assault and succumbed on 29 December, 2012. 

A trial court had sent the juvenile convict to a reform facility for three years, while the five others were sentenced to death, a verdict upheld by the high court. Of the five adult convicts, one was found dead in Tihar Jail on 11 March. The police suspect it to be a suicide.