The parents of the victim, whom AFP is also not naming in accordance with Indian law, were present inside the small courtroom on Thursday.
They have called for the killers of their daughter to be hanged and have criticised what they see as the leniency of the juvenile justice system, which seeks to reform rather than punish criminals under 18.
A sentence of three years' detention for the teenager would likely cause further public anger in India where the suspects, some of whom have been beaten up in jail, are hate figures.
About sixty journalists from the domestic and international media gathered outside the court on Thursday.
India's legal system and police forces have faced intense scrutiny over their failure to curb violence against women following the Delhi gang-rape and other cases.
Reports of horrifying sexual assaults are still a daily feature of Indian newspapers and the number of recorded crimes against women has rocketed since the December 16 case.
One of the main consequences of the case, say campaigners, has been that women feel more emboldened to report crimes against them, while criticism of the police has made officers more sensitive when dealing with such cases.
A court in central India last week sentenced six men to life in prison for the gang-rape and robbery of a 39-year-old Swiss woman cyclist who was holidaying in the country in March.
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