A forensic biologist told an Italian court today the DNA of Amanda Knox and her slain roommate was found on a knife that police believe is the murder weapon.
Patrizia Stefanoni also testified that several blood samples were found in which the DNA of Knox and her former roommate Meredith Kercher were mixed together.
Stefanoni's daylong testimony came as the prosecution neared the end of its case in a drawn-out trial that began in January.
Kercher, 21, was found stabbed to death on Nov. 2, 2007 in the apartment she shared with Knox and two Italian women. Knox, 21 and her former Italian boyfriend Raffaele Sollecito, 25, are charged with the sexual assault and murder of Kercher in what prosecutors believe was a drug-fueled sex game.
A third person, Rudy Guede, 22, has already been convicted of murder and sexual assault in the case and is serving a 30 year prison sentence.
Stefanoni testified today that Knox's DNA was found on the handle of the kitchen knife the prosecution believes is the murder weapon. This knife was found in Sollecito's house. She said Kerches's DNA was on the blade. Stefanoni said, however, that the DNA in these samples was not from blood.
Stefanoni also said that in about 20 out of over 100 hundred samples taken from the crime scene she found Knox's genetic profile, or DNA. This is not unusual since Knox lived in the cottage, but significantly, in a number of the samples Knox's DNA was mixed with Kercher's DNA.
Most of the mixed DNA from the two women was found in blood traces discovered in the bathroom. Stefanoni told the court that Knox's DNA was found mixed with Kercher's in a luminol-enhanced bare footprint in the hallway outside Kercher's room,and in a luminol-enhanced spot found in the room of housemate Filomena Romanelli.
When the murder was discovered, Romanelli's room appeared to have been broken into. Her window was shattered and a large rock was found on the floor. Nothing was stolen, however, and investigators accuse Knox and Sollecito of faking the break-in after murdering Kercher.
In the small bathroom that Knox and Kercher shared, investigators found numerous spots of blood, including on the sink, the toilet, the bidet, the rug, the light-switch and the door jamb. Three of these blood stains – one on the edge of the sink, the one on the drain of the bidet, and one on a Q-tip box - contained the mixed DNA of Kercher and Knox
The significance of the mixed DNA was not explained in court, but in past reports the prosecution has theorized that Knox used that bathroom to wash-up after the murder, and due to a nose-bleed or some other injury, her blood mixed with that of the victim.
Knox's defense, however, has mentioned the possibility that it could be menstrual blood or blood from Knox's ear, which she had recently pierced. Knox had taken a shower in that bathroom the morning after the murder, before Kercher's murder had been discovered.
The DNA of Sollecito was found only in two samples out of the many taken in the house, one on a cigarette butt in the kitchen, and on the hook of Kercher's bra, mixed with Kercher's DNA.