Amanda Knox and Raffaele Sollecito are charged with murder and sexual violence in the 2007 slaying of Knox's roommate, Meredith Kercher, in Perugia. They deny wrongdoing.
In her closing remarks Saturday, prosecutor Manuela Comodi said evidence presented during the trial had shown that the defendants' cell phones were switched off the night of the crime, making their whereabouts impossible to trace.
Comodi also recalled testimony by expert witnesses who said Sollecito's computer had not been used during the hours Kercher was stabbed to death.
According to Knox, who took the stand last June, the two suspects went to Sollecito's place to watch a movie on his computer on Nov. 1 and spent the night there, smoking pot and having sex.
The Briton's body was found on the morning of Nov. 2 in the apartment she shared with Knox.
The 21-year-old woman is believed to have died between 9 p.m. and 11 p.m. on Nov. 1, based on the autopsy and the accounts of friends with whom she had eaten dinner that night, according to court documents.
Prosecutors were expected to make the sentencing requests later Saturday. A verdict is expected in early December.
Prosecutors argued Friday that Kercher was killed during a drug-fueled sex game. They said Knox had a growing hatred for the victim and killed her, together with Sollecito and a third man, under "the fumes of drugs and possibly alcohol."
Rudy Hermann Guede from Ivory Coast was sentenced to 30 years in prison last year for the killing. He is appealing his conviction.
