Lead prosecutor Giuliano Mignini said Amanda Knox of Seattle and her Italian ex-boyfriend Raffaele Sollecito broke a window in a bedroom of the apartment that Knox shared with victim Meredith Kercher.
A stone was found in one of the bedrooms, and witnesses testified that shattered glass was found all over clothes lying on the floor, suggesting the window was broken after the room was messed up.
"The key to the mystery is in that room," Mignini said, adding that it would be nearly impossible to climb that window and enter without hurting oneself and leaving blood traces on the shattered glass.
Also, he argued, that window was the most exposed of the apartment, making it an unlikely choice for a burglar. Nothing in the room with the broken glass, which belonged to one of Knox's and Kercher's roommates, was reported missing, Mignini noted.
"All of this was done to channel suspicions on a stranger, and divert them from those who had the apartment keys," he said.
Knox and Sollecito are charged with murder and sexual violence in the 2007 killing of Knox's roommate Meredith Kercher in the central Italian town of Perugia. They deny wrongdoing.
Both have been jailed for more than two years and appeared to be tense as they sat in court Friday.
Prosecutors were expected to formally make their sentencing requests to the eight-member jury Saturday, while a verdict is expected in early December. Knox and Sollecito could face Italy's stiffest punishment, life imprisonment, if convicted of murder.
Mignini went on to reconstruct what he says happened the night of Nov. 1, 2007, when the 21-year-old Kercher was slain. He recalled previous testimony and mentioned phone records to draw a picture of Knox's and Sollecito's movements the night of the murder.
Prosecutors say Kercher was killed during what began as a sex game.
A third man, Ivory Coast national Rudy Hermann Guede, was sentenced to 30 years in prison last year for Kercher's murder in a fast-track trial he was granted at his request. He also denies wrongdoing and is appealing his conviction.
The 22-year-old Knox maintains she spent the night of the murder at Sollecito's house in Perugia. The 25-year-old Sollecito has said he was home working at his computer that night. He said he does not remember if Knox spent the whole night with him or just part of it.
Defense lawyers for Knox and Sollecito are working on the theory that Guede was the sole attacker.