Knox, the American student convicted of murder four years ago, appeared relaxed and even giggled at one point as her other lawyer, Luciano Ghirga, ridiculed a prosecution witness, covering her mouth with her hand as she tried to quickly regain her composure.
Carlo Dalla Vedova urged the court not to be afraid to correct a mistake.
"That's exactly why we have appeals - courts can make mistakes," he said. "Nobody is infallible."
Knox has spent more than 1,100 days in prison for the death of Mereditch Kercher, a British student in Perugia. She has been sentenced to 26 years in prison, while co-defendant Raffaele Sollecito was sentenced to 25 years.
Dalla Vedova said investigators were hasty in their conclusions, and he maintained that a court-ordered review of DNA had demolished much of the prosecution's case.
"Today there's very little left," he said. "A clue is not enough."
Kercher was stabbed to death in what prosecutors say had begun as a sexual assault. Knox and Sollecito insist they spent the night at his house.
Their defense lawyers maintain that Rudy Hermann Guede from Ivory Coast, is the sole killer. Guede has also been convicted and is serving a 16-year term. But prosecutors say that bruises and a lack of defensive wounds on Kercher's body prove that there was more than one aggressor holding her into submission.
Knox's family members are in Italy for the trial and had an emotional visit with her in prison.
"We visited her yesterday and she was rather anxious. But it was also the first time all my four daughters have been together for two years," Curt Knox, the defendant's father, said.
The highly anticipated verdict in the appeals case is expected Monday.
The Associated Press contributed to this report.