NEW DELHI - Three of the men accused of raping and murdering an Indian student in a case that has provoked widespread anger with the government and police will plead not guilty, their lawyer said on Wednesday, citing lapses in the police investigation.

The 23-year-old physiotherapy student died two weeks after being beaten and gang-raped on a moving bus in New Delhi, then thrown bleeding onto the street. Protests followed, along with a fierce public debate over the failure of authorities to stem violence against women.

Five men are facing various charges including murder, rape and abduction. A sixth suspect is being investigated separately to determine if he is below the age of 18, as he says he is.

Lawyer Manohar Lal Sharma, who is representing the bus driver, who is the main accused, his brother and another man, said he was keen for the case to go to trial so that the evidence police had presented could be tested in court.

"We will plead not guilty. We want this to go to trial," Sharma told reporters.

"We are only hearing what the police are saying. This is manipulated evidence. It's all on the basis of hearsay and presumption."

It is not known if the other two of the five accused men have a lawyer.

Charges against the sixth member of the group have not been brought while police complete an inquiry to confirm his age. If he is found to be below 18 he will be tried in a juvenile court and if convicted will go to a correctional home, not a prison, to serve a maximum term of three years.

Sharma said the police had rushed through the investigation against the five men even when they were not ready with the key detail of the age of the sixth member of the group, who lured the woman and a male friend into the bus and, according to leaked accounts, was the most brutal in the attack.

"When you have not even established the age of this person, how can you go to court bringing the charges against the others, and say your investigations are complete," Sharma said.

"We all know how police investigations are carried out in India."