Three of the men accused of raping and murdering an Indian student in a moving bus will plead not guilty to the charges, their lawyer said on Wednesday, citing lapses in the police investigation.

Five men have been charged for the assault on the woman in a case that has provoked such outrage that lawyers in the district where the case is being heard have refused to defend the men.

Manohar Lal Sharma, who will represent the bus driver and the main accused, his brother and another man, said the case must go to trial so that the evidence police have presented can be tested in court.

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

It is not yet known if two other accused men have a lawyer, while a sixth accused will be tried separately because he is a minor.