PERUGIA, Italy - Amanda Knox won an important victory in her appeal of her murder conviction in Italy on Saturday, when a court ruled that it will allow an independent review of crucial DNA evidence after defense claims that samples were inconclusive and possibly contaminated.

The lower court trial, which convicted the American student a year ago and sentenced her to 26 years in an Italian prison, had rejected a similar defense request for an outside review of DNA found on the bra clasp of the victim, her British roommate Meredith Kercher, and on a knife the prosecution alleged was used in the fatal stabbing.

Kercher's body was found in a pool of blood on Nov. 2, 2007, her throat slit in the apartment she shared with Knox. Forensic experts said she had been killed the night before.

Saturday, Knox burst into tears, in a sign of a release of tension, said her stepfather, Chris Mellas. "She's a happy mess," he said, smiling.

She was convicted of sexually assaulting and murdering Kercher in the rented house they shared in the university town of Perugia, where both were studying. The codefendant in the appeals trial is Knox's ex-boyfriend, Raffaele Sollecito, an Italian who was convicted of the same charges and sentenced to 25 years. Both deny any wrongdoing.

Prosecutors maintain that Sollecito's DNA was found on the bra clasp and that Knox's DNA was found on the knife handle and Kercher's DNA on the blade. The defense maintains that DNA traces presented at the first trial were inconclusive and also contends they might have been contaminated when they were analyzed.

In another gain for the defense, the court said it would allow several witnesses who the defense hopes will refute testimony that placed Knox and Sollecito near the house on the night Kercher was killed.