The only surviving suspected attacker from last year's siege of Mumbai could face the death penalty after a court ruled that he would be tried as an adult.
Defence lawyers had called for Mohammed Ajmal Kasab's case to be transferred to a juvenile court as he was under the age of 17.
But Judge ML Tahiliyani said "forensic experts have corroborated evidence of witnesses... [and] there is no doubt that Kasab was not a minor," the Press Trust of India news agency reported on Saturday.
Indian medical experts reportedly declared that Kasab was at least 20-years-old after examining his teeth and x-rays of his bones.
The judge also accepted evidence from a superintendent of the jail where Kasab has been held and a doctor who both said the suspect had told them he was 21-years-old, the Press Trust of India reported.
"I am made to believe by the witnesses examined that the accused was 21 years at the time of attack and his date of birth is September 13, as mentioned by him to his jailer ... and the doctor who examined him," Tahiliyani was quoted as saying.
Prosecutors say Kasab, a Pakistani national, was one of 10 attackers who rampaged through India's financial capital last November, leaving at 166 people dead and 304 injured.
He faces a string of charges including "waging war" on India, murder, attempted murder and kidnapping.