A division bench of justices R D Dhanuka and Prithviraj Chavan had held Samson D'Souza guilty on July 17 for "culpable homicide not amounting to murder" and molestation, among other charges.
The bench had overturned the verdict of Goa Children's Court which had acquitted D'Souza, but upheld the acquittal of second accused Placido Carvalho.
Scarlett, 15, who was holidaying in Goa with her mother and siblings, was found dead on the popular beach on February 18, 2008. The cause of death, according to the autopsy report, was drowning.
Initial investigation was conducted by Goa Police. However, Scarlett's mother Fiona Mackeown alleged that the probe was "shabby".
The state government then handed over the case to the Central Bureau of Investigation.
D'Souza, who worked at a beach-side shack, and Carvalho, a suspected drug dealer, were first arrested, based on witnesses' accounts, by Goa Police.
The CBI named both of them in its charge sheet, claiming they drugged the girl and sexually abused her.
Trial court judge Vandana Tendulkar acquitted both the men in 2016, a verdict the CBI challenged.
The Goa bench of the high court two days ago held D'Souza guilty under IPC sections 328 (for administering drugs), 354 (outraging modesty), 304 (culpable homicide not amounting murder) and 201 (destruction of evidence) and for child abuse under section 8 (2) of the Goa Children's Act.
D'Souza was present in the courtroom Friday. His lawyer sought a stay to the sentence for 12 weeks so that he could file an appeal in the Supreme Court.
The bench rejected the plea. D'Souza was sent to judicial custody and would be shifted to a prison at Colvale in North Goa district.
Senior lawyer Vikram Varma, who represented Scarlett's mother, said justice has been finally delivered.
The sentence would send a signal that law and order in Goa's beaches should not be violated, he said.
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