Vikram Varma, a lawyer representing Keeling's mother, Fiona MacKeown, said in Panaji, the capital of Goa state, he was happy with the court's decision. It has taken a lot of time, but justice has been done, he said.
The teenager's death caused outrage among the millions of tourists who throng the beaches of the resort city on India's west coast. Police originally said Keeling had drowned after taking drugs, but changed their story after her mother complained. D'Souza's sentencing comes after an 11-year battle for justice by Scarlett's mother.
A trial court acquitted both of the accused in 2016 saying there was not enough evidence to convict them. The High Court took up the case in 2017 after an appeal by the Central Bureau of Investigation, India's FBI.
Under Indian laws, both the accused and prosecutors can appeal a trial court's verdict to the High Court and the Supreme Court. D'Souza and prosecutors can still appeal his sentence to the Supreme Court, and prosecutors can still appeal the acquittal of the second suspect as well.