A local barman Samson D'Souza, working on a shack, and one Placido Carvalho, also a local, were tried on charges of drugging, sexually abusing and leaving the teenager to die on the beach, where her body was found on February 18, 2008.
Goa Children's Court president Vandana Tendulkar said the verdict would be pronounced on September 23 with the final arguments in the case concluding today after two days.
The prosecution has examined 31 witnesses, including the mother of the deceased, Fiona Mackeown during the trial.
Mackeown has flown to Goa from Davon (UK) to be present in the court. She has already deposed before the court.
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The case, initially investigated by Goa Police, was later handed over to CBI after Scarlett's family accused the local police of hushing up the matter.
CBI Special Public Prosecutor Ejaz Khan banked his arguments on the 'last-seen-theory' as Scarlett was allegedly seen with Samson, three hours before her body was found on the shore.
"The accused (Samson) in his statement has not revealed what has happened during the three hours after he was last seen with the girl. The accused is trying to deny his presence at the scene," Khan said.
"Both the accused should be punished. One committed the offence, and other helped him hiding it," the SPP argued.
He dismissed the contention that CBI framed Samson under "some influence".
"Common people like a barman cannot pressurise CBI which is a national agency of repute. What benefit will CBI get by entangling a barman?" Khan told court.
Defence lawyer Mervin D'Souza said Samson was being targeted as he was defenceless.
D'Souza said the "death of the girl (Scarlett) was
"In (Scarlett's) autopsy, morphine was found along with cocaine in her body, which indicates that she was already intoxicated when she arrived at the shack where Samson was working and Placido was sitting," he said.
He said the investigating agencies (Goa Police and CBI) were "purposely blind to the fact that she was already drugged and they failed to probe who had administered her the narcotics".
D'Souza said the detailed forensic examination by experts from Delhi-based AIIMS proved that there was no abnormality in Scarlett's brain, skull, vagina and heart, "which proves there was no scuffle by her".
He said Scarlett's lifestyle was not like that of a normal child in India.
However, the judge interjected, saying this aspect (about lifestyle) has nothing to do with the current case.
The defence has claimed that Scarlett's death was caused by "external forces".
Placido's advocate Pravin Naik said there was no witness on record to state that his client had administered drugs to Scarlett in the shack where she was last seen before her death.
The case had grabbed international attention as Britishers used to be the largest number of tourists visiting Goa.
Scarlett's mother had said on Tuesday, "I do hope that justice would be done."
She had said she wanted the two accused to be charged with murder "because I believe she was murdered, but the charge is of culpable homicide, which still is a good enough".
Accusing the erstwhile Congress government of supporting the police in hushing up the case, she blamed the prosecution for its "failure" to ensure deposition of a crucial eyewitness Michael Mannion, a British national, before the court.