A teenager on remand at Barwon Prison has been refused bail, despite a Supreme Court judge saying he assumed his human rights were being breached in a "less than satisfactory" situation.
The 16-year-old, referred to as JC, has been on remand at the Grevillea unit of the maximum-security adult prison for about two months.
He faces a range of criminal charges.
Prosecutor Cameron Gauld earlier argued that JC's bad behaviour had escalated in recent weeks, culminating in a "rampage of damage" to washing machines, driers and a television in the common area of the unit, with criminal charges expected to be laid.
JC had also been abusive to staff members, he said.
Mr Gauld said: "If all these are to occur when he knows he's being watched, the concern...is what (will he do) when he's not monitored and constantly supervised?"
Justice James Elliott said on Friday that despite his "misgivings" about the conditions in which JC was being held, the teenager posed an "unacceptable risk of committing offences while on bail and endangering members of the public".
Justice Elliott said he made his decision on the assumption that the youth's human rights continued to be breached at the Grevillea unit, but stressed that this was not a formal legal finding of a breach.
The judge, who personally inspected the unit last month, said that the conditions for children were "far from ideal."
He said that the government's plans to improve the facilities there showed that at least when he visited the prison "the situation was less than satisfactory".
Seventeen children were being held on remand at the Grevillea unit on Friday, the court heard.
JC previously told the judge he had trouble sleeping at night, and could hear adult prisoners through a shared wall in the Grevillea unit, the court heard.
The teenager, whose behaviour was previously considered of a "gold" standard, had not seen a psychologist or his family members since being remanded at the unit.
Justice Elliott noted that Marcel Jacques, the head of operations at Grevillea, could not say when he was cross-examined whether JC's recent actions could be explained by a lack of medication.
Mr Gauld told the court that JC's continued detention was justified given his pending criminal charges, including one of armed robbery. While no witnesses had positively identified JC, there was likely to be more evidence as the police investigation continued, he said.
JC is expected to plead guilty to a number of charges including unlawful assault and wilful damage in the Children's Court next week, after which the court heard he could be moved to Malmsbury youth justice centre.
Negotiations continued on other charges, including armed robbery and committing an indictable offence while on bail, the court heard.
The Andrews government began moving dozens of children from three youth justice centres to Barwon prison after a riot at Parkville youth justice precinct damaged 60 beds there in November.
The state reclassified the unit as a youth justice and remand centre last week, after the Court of Appeal ordered it remove the children to a lawfully established centre.
Children's Minister Jenny Mikakos has said that the centre had to be established quickly to house children after the riot. She said the government had since improved health services there, built a visitors' centre and increased the hours of schooling available to children held there.
A government spokesman said that the decision was a matter for the court.
He said: "Barwon Prison's Grevillea Unit was lawfully established and is safe, secure and functioning appropriately as a youth justice facility and remand centre."