The prosecutors also said Knox had confessed during police questioning - but she later said she had been struck by officers during her interrogation.
They said she had falsely accused Mr Lumumba to hide her guilt.
Knox's alibi was also challenged. She said she had been at Sollecito's house on the night of the murder, they had smoked cannabis, had sex and fallen asleep.
Prosecutors said none of it could be proved.
And then there was Knox's behaviour at the police station while waiting to talk to investigators.
Police and friends testified that Knox had performed cartwheels, done the splits and giggled with Sollecito.
Knox would later say it was her way of dealing with the stress and grief of the situation.
The prosecution also said Sollecito's DNA had been found at the murder scene, on the clasp of the bra worn by Miss Kercher.
Sollecito's defence team said the evidence was contaminated and did not stand up.
Prosecutors also questioned Sollecito's claims he had been at home downloading Japanese cartoons on the internet at the time of the killing. They said records from his internet service provider did not support that.