The police official who conducted the original investigation in the Amanda Knox case defended her standards Monday, after an independent review harshly criticized the evidence used to convict the American student of murdering her British roommate.
Patrizia Stefanoni took the stand as Knox's appeals trial resumed after the summer recess. A verdict is expected by the end of the month.
Knox and her co-defendant and one-time boyfriend, Raffaele Sollecito, were convicted of sexually assaulting and killing Meredith Kercher in the apartment that Knox and the 21-year-old Briton shared while studying in Perugia. Knox was sentenced to 26 years in prison; Sollecito to 25. Both deny wrongdoing and have appealed the Dec. 29 verdict.
An independent review of DNA traces in the case found that much of the evidence collected in the original investigation fell below international standards and may have led to contamination of the samples. The review especially focused on some traces of DNA linking the defendants to the crime, and concluded that due to the risk of contamination and the low amounts of DNA used for the testing it was impossible to extract a genetic profile with any certainty.
In the first trial, prosecutors maintained that Knox's DNA was found on the knife's handle and Kercher's DNA was found on the blade. They also say Sollecito's DNA was found on the clasp of Kercher's bra, mixed with the victim's.
Carla Vecchiotti, one expert questioned Monday over the extraction of DNA profiles from the bra clasp, said the data was so mixed that a very high number of genetic profiles could be extracted, depending how one combined the data.
"I could find yours, too," Vecchiotti told the presiding judge. "I'm there, too," she said, adding that some data was compatible with her own DNA. She said Kercher's profile was the only certain one.
The findings have boosted the defendants' efforts to be cleared and gain freedom after almost four years in prison.
Curt Knox, the defendant's father, said he was hopeful that the case was turning in his daughter's direction.
"The independent experts have done a very good job evaluating the information," he said. "I don't see it breaking down at this point. I see it's been good for Amanda and Raffaele."
Giulia Bongiorno, a lawyer for Sollecito, said DNA can be "formidable evidence" but not with such a mixed, confusing trace.
"Poorly collected DNA can lead to an error of justice," she told reporters during a break in the proceedings.
The two independent experts were appointed by the appeals court at the defense's request. Over two sessions of fierce cross-examination, both the prosecutors and a lawyer representing the Kercher family have sought to undermine the experts' testimony and insisted that the evidence could stand.
Stefanoni, the forensic police officer, countered some of the points made in the review, saying that DNA analyses were carried out from behind a glass wall to avoid the risk of contamination. She also said some of the standard protocols cited by the experts were published after she finished her report in May 2008.
Using some of the 119 slides she said she had prepared, she challenged the experts' finding over DNA quantity, analysis and evidence collection techniques. Her testimony will continue Tuesday.
The DNA review has dominated recent hearings in the 10-month appeals trial.
Just before the trial resumed, Kercher's sister issued a letter asking the appeals court to assess "every single (piece) of evidence" so justice can be done. The Kercher family insisted they still had faith in the Perugia police, investigators and the court, but also expressed worry over the evidence review.
"We find it extremely difficult to comprehend how the evidence that was so carefully developed and presented in the first hearing was valid, yet how it now seems to carry a slight chance it will become irrelevant," Stephanie Kercher said in the letter.
"We ask that the Court of Appeal assess every single (piece) of evidence, both scientific and circumstantial, as well as any witnesses who have taken the stand independently of any other information or media," she wrote.
The Kercher family has kept a low profile throughout the headline-grabbing case. The letter, released through the family's lawyer Francesco Maresca, represented a rare break in their silence.
"Meredith has been forgotten because she is no longer with us, yet this should be about her and what really happened on that tragic evening," Stephanie Kercher lamented in the letter.
Knox has been the center of attention since her arrest on Nov. 6, 2007 — four days after Kercher's body was found in a pool of blood at the apartment. Knox has been described both as an angel-faced ruthless killer and as an innocent girl caught in an Italian judicial nightmare.
Both Knox, 24, and Sollecito, 27, attended the session Monday.
A third person, Rudy Hermann Guede of the Ivory Coast, also has been convicted of Kercher's murder in a separate proceeding. Italy's highest criminal court has upheld Guede's conviction and his 16-year-prison sentence. Guede denies wrongdoing.