When Caltagirone was asked during cross-examination by prosecutor Giuliano Mignini whether the cartwheels and stretches Knox did in the police station that night did not indicate a relaxed frame of mind, he responded that "the cartwheels were certainly incongruous" but he felt they actually "reflected great stress" and by trying to relax, he said, she trying to "defend herself from such a stressful situation."
Walter Patumi, a coroner on the Knox defense team, also testified today. He discussed the knife that investigators believe is the murder weapon, reiterating what other defense experts have already said - that the large kitchen knife is not compatible with Kercher's wounds, and that the trace of Kercher's DNA police said they found on the blade is too small to be reliable.
Both Knox and Sollecito were in court on Friday. Both insist they are innocent and neither of them has missed a hearing.
A third person, Ivory Coast native Rudy Guede, has already been convicted of the murder. Prosecutors insist Guede, Knox and Sollecito killed Kercher during a drug fueled sex game gone wrong.
Also in court was Knox's father, Curt Knox, who has been present at a dozen hearings since the trial began on Jan. 16.
"I think today's hearing went very well," Curt Knox told ABC News. "Caltagirone brought up the fact that Amanda was interrogated by police for 41 hours over four days, and that that can lead to potential confusion in a high-intensity interrogation," he said. "It tells us that they took advantage of a very young girl, in the course of continuous, continuous, continuous interrogation," Knox added.
The trial continues on Saturday with the last two witnesses for the defense, after which court will meet again in Oct. 2 to hear possible requests for further evidence to be presented or witnesses to be heard again. There is a likelihood that defense teams will request a review of the scientific evidence by an independent expert, given the conflicting evidence presented in the course of the trial.
"I don't see how the judges and jury can make a decision without an independent review," Curt Knox said outside of court. And though such a review could postpone a verdict for months, Knox said that it would be worth it. "If it takes two months to get out with the truth and the facts," he said, "then it is well worth the wait, versus two more years it would take to appeal."
A neuro-psychologist called to testify on behalf of American murder suspect Amanda Knox told an Italian court today that stress can affect memory and cause people to have "false recollections."
Professor Carlo Caltagirone explained how stress can have a negative effect on memory, a phenomenon that he said has been studied extensively in both regular and forensic medicine.
"All aspects of memory can be modified by stress," Caltagirone told the court in Perugia, Italy. "And certain circumstances can produce false recollections in perfectly normal people who are completely in good faith."
Knox, 22, who is accused, along with her former Italian boyfriend Raffaele Sollecito, 25, of murdering her roommate Meredith Kercher, 21, gave police conflicting versions of events in the days after Nov. 2, 2007 when Kercher's body was found semi-naked in a pool of blood in the apartment the two girls shared on the outskirts of Perugia.