Amanda Knox Case Turns on Sharply Disputed Forensics

When summations begin Friday in the trial accusing Amanda Knox of murdering her British roommate, prosecutors and defense attorneys will have the testimony of 130 witnesses and experts over the past eight months to highlight in order to prove the guilt or innocence of the Seattle exchange student.

The case is built on forensic evidence which is being sharply contested, and a mountain of circumstantial evidence.

It is lacking, however, a witness who can put Knox and her co-defendant and former boyfriend Raffaele Sollecito at the scene of the crime - the cottage in Perugia, Italy, when Meredith Kercher was slain on Nov. 1, 2007. (A third person, Ivory Coast native Rudy Guede, has already been convicted of taking part in the murder.)

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What the prosecution claims is the murder weapon is also being sharply contested.

And there is a question of motive. Prosecutors state that Kercher died in the course of a sexual encounter that went bad when Kercher refused to participate.

Knox is a sweet-faced Seattle, Wash., student who was 20 at the time of the homicide, hardly the profile of a grisly murderer.

But her good looks have helped attract often lurid coverage of the case by the Italian and international media which has eagerly followed her statements, court demeanor, and trial tactics. It is unclear whether that could have an effect on the jury's deliberations in Italy where juries are not isolated.

When prosecutor Giuliano Mignini addresses the jury, he will argue that the case is a "puzzle" in which all the elements come together to prove their guilt. He will attempt to put that puzzle together for the jury, while Knox's lawyers will try to show that the puzzle pieces don't fit.

What will be challenged most in the courtroom will be over the forensic evidence.

The most incriminating items, if they hold up in the minds of the six jurors and two judges, are a kitchen knife from Sollecito's home and Kercher's bra clasp.

Investigators identified Kercher's DNA on the blade and Knox's DNA on the handle of the 6.5 inch long knife. The prosecution claims this is the murder weapon and the DNA proves that Knox is the one who wielded it.

DNA Evidence in Amanda Knox Case Is Disputed

But the amount of the biological material found on the blade was so small that the DNA test could not be repeated, and it tested negative for blood. Defense witnesses also argued that the 6.5-inch knife was not compatible with some of Kercher's wounds.

A fragment of Kercher's bra clasp is the strongest piece of evidence linking Sollecito to the murder. The piece of the bra with the hook fell off when the bra was cut from Kercher's body by her assailant, and Sollecito's DNA was found on the metal hook.

The clasp was identified and photographed when forensic scientists analysed the crime scene, but it was not taken into evidence until six weeks later when investigators realized it was missing. The house had been turned upside down in a police search in the meantime.

Sollecito's lawyers argued that the crime scene had been contaminated, and that the tiny clasp had picked up Sollecito's DNA in the mess.

The bra clasp is the only evidence that places Sollecito in the room where Kercher was murdered, and not a single trace was found that puts Knox in the room – no fingerprints, footprints, DNA.

There is plenty of evidence putting Knox and Sollecito in other parts of the cottage, including a bloody footprint found on the mat in one of the bathrooms. The footprint was said to be "absolutely compatible" with Sollecito's foot by a forensic physicist for the prosecution. An expert for Sollecito said it matched Guede's foot.

Experts for both sides, however, said the print was not a positive identification because it lacked the actual rings of a finger or toe print that are specific to an individual.

Three blood stains found in that same bathroom, which Knox shared with Kercher, contained Knox's DNA mixed with Kercher's. Prosecutors will argue that the reason is that Knox washed the blood from her hands in that bathroom. Defense lawyers will say it is normal for both girl's DNA to be in a bathroom they shared.

A great amount of circumstantial evidence was presented in the course of the trial, and it promises to be a big part of closing arguments for prosecutor Mignini.

Problems With Amanda Knox's Defense

This includes:

Knox's statements under interrogation.

In the course of an overnight interrogation four days after the murder, Knox gave a confused statement in which she said she seemed to recall she was in the kitchen when Kercher was killed, covering her hears to block out Kercher's screams.

Because the statement was made without a lawyer, it was thrown out by the Italian supreme court. What can be used, however, is a confused written statement Knox gave police the next morning in which she wrote that she "stood by" her statements, but that events she described "seemed more unreal to her" than her previous version of events, that she spent the night with Sollecito.

When Knox testified in court for two days last June, she said police put enormous pressure on her during what she described as a harrowing interrogation, calling her a liar, hitting her on the head, and suggesting Lumumba's name to her.

The alibi.

Knox and Sollecito claim they were together the night of the murder, but there are inconsistencies with their stories.

The two say they spent the evening at Sollecito's home watching a movie, and using the computer, but police computer experts say there was no human interaction on the computer after 9 p.m. that night.

Sollecito claims to have called his father during that evening, but phone records turned up no evidence of the call. And police believe it is strange that both Knox and Sollecito turned off their cell phones about 9 p.m. on the night of the murder, something they did not usually do.

There were also discrepancies on whether they spent the night together. On Nov. 5 Sollecito told police during a second grilling that he had gone home, but Knox had stayed in town until 1 a.m. Sollecito later gave yet another version, saying he did not remember if Knox had gone out or not that night.

Strange behavior

The prosecutors have made much of what they consider the strange "cold and contradictory" behavior of Knox and Sollecito in the aftermath of the murder.

Numerous witnesses – including police officers and Knox's Italian housemates - testified that they appeared cold and unaffected, that they did not cry, that they giggled and cuddled in the police station, and Knox even did gymnastics there.

Perhaps the one thing that most puzzled investigators, and which provoked a series of questions from the judge when Knox was on the stand, was why when she went back to her house on the morning of Nov. 2 and found the front door wide open, no one home, Kercher's door shut, and blood in the bathroom, yet she went ahead and took a shower before alerting anyone that something was amiss.

Closing arguments begin Friday with one day alotted for each of the two prosecutors on the case. Mignini will likely present the general outlines of the case and the circumstantial evidence while Manuela Comodi will focus on the forensics.

Both are confident their evidence is strong. A verdict is expected around Dec. 4.