Vikram Varma, who is acting for Fiona MacKeown, Scarlett's mother, cited a new postmortem report from Goa’s chief pathologist, which also revealed that the alcohol and drugs in her body were not sufficient to kill her.
The new report, prepared in Goa’s state capital Panjim by forensic scientist Dr Silvano Sapeco, is partly based on the results of a stomach analysis.
It said: “The findings in this case are consistent with exact (text book) picture for homicidal drowning in shallow water.”
The report also said cuts and bruises on the body showed she had fought against her killers.
The new claims directly contradict the police account of the events leading up to the death of Scarlett, 15.
Goa police initially tried to convince Ms MacKeown that her daughter’s death last month was due to accidental drowning.
After a vigorous campaign by Ms MacKeown, a second autopsy was ordered which confirmed her belief that Scarlett had been raped and murdered.
“The reports show that Scarlett fought back,” said Mr Varma. “It is also clear that her head was held under shallow water for five to 10 minutes.
"This is consistent with a forensic description of homicidal drowning. This shows that we have been lied to all along.”
Ms MacKeown said she had been "proved right" by the latest findings and accused the Goan police of a "cover-up".
"This is something I’ve been saying from the beginning," she said.
"I’ve said there’s been a cover-up from the start. I haven’t been contacted by the police once. I want the police brought to justice."
She reiterated her calls for a full independent investigation by the Indian Central Bureau of Investigation (ICBI) into the way the case has been handled.
