charge sheet against him before a Juvenile Justice Board (JJB), a sign that they are prepared to settle for a light sentence for the youngster - a maximum of three years in a reformatory for a particularly vicious gang rape that resulted in the victim's death.
Senior police officials told HT they were not optimistic of overturning a JJB finding on January 28 that the accused individual was a juvenile.
Until this point, the police have maintained that they are exploring all options to ensure the youngster, described by them as the most brutal of the six assailants, gets the maximum punishment.
"It's a Catch-22 situation. If we appeal, we will be asked for proof we don't have, and we can't appeal for a bone test given that it has an error margin of at least six months," said a senior cop.
"We don't have much hope."
The key evidence in favour of the attacker is his school-leaving certificate, which shows him to be 17 years and 6 months old.
The weightage given to this evidence is underlined by the fact that school-leaving certificates have been used to nail two of the other five accused, who had also tried to use the juvenile route to wriggle out of a potential death sentence.
While one attacker, Vinay, was earlier reported to have appealed that he was juvenile, it has emerged that another, Pawan, had also tried the same ruse.
The court of the metropolitan magistrate and the special sessions court had both rejected the claims.
The father of the 23-year old victim, who had earlier said he would challenge the JJB's ruling on the juvenile status, reacted in a measured way on Thursday.
"We will wait and watch. We don't want a situation where the other five accused get a breather because of too much focus on the juvenile," he told HT.
The JJB is likely to hear arguments for framing the charges starting February 14.
The board had dismissed the police's plea for a bone test, a procedure that is often used to determine the age of an individual, because the school-leaving document was available. As per school records, the boy's date of birth is June 4, 1995.
On December 16, the victim, who was with her male friend, was gang-raped and assaulted by the six men on a moving bus in south Delhi.
The other five accused individuals have already been charge-sheeted and are being tried by a fast-track court for gang rape, murder and abduction.