Amanda Knox Expert Disputes Murder Weapon

A medical examiner hired by Amanda Knox gave grisly testimony today about how her roommate was likely killed, and concluded that the knife presented by the prosecution could not be the murder weapon.

Medical examiner Carlo Torre also told the court he believed only one knife was used in the crime, and that only one person was involved in the killing.

Ivory Coast native Rudy Guede has already been convicted for taking part in the death of Knox's roommate Meredith Kercher and was sentenced to 30 years in prison.

Knox, 21, of Seattle, has been on trial in Perugia, Italy, since January, accused, along with her Italian former boyfriend Raffaele Sollecito, of sexually assaulting and murdering Kercher, a 21-year-old British exchange student with whom she shared a scenic cottage with a view of the Umbrian hills. Kercher was found semi-naked with her throat slit Nov. 2, 2007.

Torre, hired as a consultant by Knox's defense team, told the court today that the knife that investigators believe is the murder weapon -- a kitchen knife with a 12-inch blade found in Sollecito's kitchen -- was not compatible with some of the wounds found on Kercher. Investigators have said that Knox's DNA was found on the handle of the knife, and that traces of Kercher's DNA was found on the blade.

Torre used autopsy photos to illustrate his points and brought a styrofoam head on which he demonstrated the cuts to the victim's throat. Because of the graphic nature of the testimony, the judge decided that part of the hearing should take place behind closed doors.

Everyone except the legal teams and parents of the defendants were asked to leave the room. Knox's sister Deanna, 20, and her close friend, Madison Paxton, who were in court to support Knox along with her mother Edda Mellas, also had to leave. Ashley Knox, 14, Amanda's half-sister, is not allowed in court at all, because she is a minor.

Ashley told ABC News she was disappointed she couldn't be in court. "I was sad I couldn't see her for that extra time, but I know she'll do good," said Ashley.

Mellas told reporters that the images shown in court were not particularly gruesome, just close-up photographs of the wounds. Amanda Knox prefers not to look at them, and usually writes or doodles when they are shown, her mother said.

Torre, who is a renowned forensic consultant in Italy and has worked on a number of high-profile cases, told the judges and jurors today he believes the three cuts to Kercher's throat were made by a smaller knife, with a blade that was, at most, 3 inches long. He feels the the big wide slash to her throat was made by the sawing action of the smaller knife.

Amanda Knox Expert Disputes Murder Weapon Theory

"The smaller wound is absolutely incompatible with the knife in question," he testified. "For the larger wound, I cannot rule it out, but it could have been made by a myriad of knives," he added in reply to a question from the prosecutor. "Everything leads me to believe that that is not the murder weapon," he said, referring to the knife found in Sollecito's home.

When asked if there could have been two knives involved, a theory put forth by the prosecution when it had to admit that the smaller wounds could not have been made by the big kitchen knife, Torre replied, "It would be the first time in history that a murder was done with two knives."

Torre, a professorial type with unruly white hair, also said the knife had an unusual "regularity" to the top edge of the blade that also seemed to have a notch on it similar to a "survival" knife of the kind used by a "Rambo."

Torre contradicted the theory of both the prosecution and the medical examiner hired by Sollecito regarding the position in which Kercher was when she was killed.

Torre said he felt Kercher was murdered when she was on her back, her head lifted "a palm and a half off the floor." Francesco Introna, Sollecito's consultant, told the court last month that Kercher was knifed from behind, a lone killer holding her chin with one hand and the knife in the other. The prosecutors also believe she was attacked from behind, but think she was held by Sollecito and Guede, with Knox wielding the knife.

Torre said it was "more logical to think" that she was killed from the front, and that "it seems difficult that it was from behind," but did not totally discount the idea.

Torre also pointed out that the luminol footprints that investigators say are of Knox's bare feet cannot be because Knox's second toe is longer than her big toe, and that characteristic is not apparent in the lumino-enhanced prints. He also pointed out that the bare footprints of the other two women who lived in the house were not taken for comparison, nor were those of the victim.

In another important affirmation, Torre told the court "there is not a single element that leads one to think more than one person could have comitted the crime." The defenses of both defendants believe the murder was the work of a single thief turned killer, Guede, according to Sollecito's lawyer Luca Maori.

Amanda Knox to Celebrate Birthday in Jail

At the end of the day, Knox's mother told reporters she felt the hearing had gone well, though she does not understand the proceedings in Italian. "Everyone seems happy with how it went," she said. When she was able to see her daughter briefly at the end of the hearing, Amanda, who understands Italian, told her the hearing was very technical, and that it had been a long day.

Knox will celebrate her 22nd birthday July 9th -- her second in prison. "She did not want to spend a second birthday in prison," Mellas told ABC News as tears filled her eyes. "But it will definitely be the last one if all is right in the world and things go the way they should."

Thursday is a visiting day in the Capanne prison, so Knox will be able to celebrate with her mother, two sisters, best friend Paxton and an aunt from Germany.

"We cannot wrap presents for her, but will be bringing her a couple of shirts for court, some CDs and books, and lots of birthday cards from family and friends," her mother said.

Sollecito, Knox's former boyfriend, has asked to be allowed to give Knox a box of chocolates for her birthday, according to his lawyer.