for "nightline" in new york. >> our thanks to elizabeth vargas. >>> and coming up, some of the hottest competition on the beach this summer isappening under water. and if you're looking for something more extreme, do not hold your breath. the stronger the rapids, the more we loved it. took some wild risks when i was young. but i was still taking a risk with my cholesterol. anyone with high cholesterol may be at increased risk of heart attack. diet and exercise weren't enough for me. i stopped kidding myself. i've been eating healthier, exercising more, and now i'm also taking lipitor. if you've been kidding yourself about high cholesterol, stop. along with diet, lipitor has been shown to lower bad cholesterol 39 to 60 percent. lipitor is fda approved to reduce the risksterol of heart attack and stroke in patients who have heart disease or risk factors for heart disease. [ female announcer ] lipitor is not for everyone, including people with liver problems and women who are nursing, pregnant or may become pregnant. you need simple blood tests to check for liver problems. tetel y

abc's "20/20" anchor elizabeth vargas has been following the case from the beginning, and elizabeth, this could set her free. >> reporter: it could, george. it is the evidence that put amanda knox behind bars. prosecutors convinced the jury that knox's dna and the dna of her dead roommatatwas found on the knife that was allegedly used in the murder. that evidence, and this entire case, is now in question. today's finding by court appointed experts that that dna at the center of this case was unreliable brought a glimmer of hope to amanda knox's mother. >> i was thrilled. the report said exactly kind of what our experts said all along that the correct procedures were not followed. they can't rule out contamination. we can't really celebrate until amanda walks out of that prison. but this is just one big step in that direction. >> reporter: amanda knox is appealing the guilty verdict that has sent her to prison for 26 years. that appeal getting a major boost from today's conclusion that the dna was either too miniscule or possibly contaminated to be used as evidence. it was 2009 when t

but first, abc's elizabeth vargas has the details. >> reporter: it was the kind of news amanda knox hadadeenting nearly four years to hear. independent, court-appointed experts have concluded that key dna evidence, which helped convict amanda, may now have been contaminated or improperly collected. >> the report said that exactly kind of what our expert said all along. that the correct procedures were not followed. >> reporter: prosecutors argue that two key pieces of evidence implicate amanda and her then 6 boyfriend, raffaele sollecito. a kitchen knife found in sollecito's apartment with both of the girls' dna and kercher's bra clasp had sollecito's dna on it. some cases it was too minuscule to even properly test. the third defendant in the case, rudy guede, who is serving a 16-year sentence for the murder, was in court earlier this week, denying testimony that he told cellmates knox and sollecito were innocent. guede's dna is all over the bedroom where the murder took place. knox's dna is nowhere to be found. she just cleaned the room of her own dna? >> t tt's what they're saying. >> not

murder conviction, for killing her roommate while studying abroad in italy. "20/20" anchor, elizabeth vargas, has been on top of this since the beginning. and has more on the key witness that will take the stand. it just goes on and on and on. >> reporter: it does, robin. robin, a key witness is rudy guede. the third person convicted of murdering meredith kercher in 2007. there has been little doubt about his guilt. unlike amanda knox and her former boyfriend, his dna is all over the crime scene. today, he'll deny reports that he told fellow inmates that knox and her boyfriend had nothing to do with the crime. guede has always admitted he was in the cottage knox shared with kercher the night she was killed, but did not arts pate in the crime, he said. instead he was listening to the ipod in the bathroom when intruders murdered meredith. amanda's mother, edda mellas is in court this morning to hear his testimony. guede's testimony is one of two key elements in this proceedings. the other independent review of crucial dna evidence. including trace evidence of kercher's dna in sollecito's apart

walking in memphis ♪ but do i really feel the way i feel ♪ >> do you know marc cohen is married to elizabeth vargasom new york. >> look at the line. i'm sorry. >> you've got to go there. they said you didn't go there. they are the nicest people in the world. they brought so many kids out. >> how fun. >> i'm wearing bobbie thomas' outfit from the other day. today i'm going to be at mendham books in mendham, new jersey. >> this is amazing to me. kim kardashian, they say she is having a baby. i spoke to chris, that is not true. brad and angie getting married. that's smaller news. >> shocking. how about breast-feeding. how do you feel about breast-feeding in public. kathie lee says it's the most natural thing in the world to feed your child, but always use discretion in public. >> hoda said yes, it is okay, as long as your child isn't over 5. >> i thought that was fair. >> i think that's still pushing it, so to speak. >>> coming up next -- who doesn't know at times "love bites." >> a new romantic comedy about love, sex, marriage, dating and anthony's weiner. [ chanting ] do it! [ chanting ] do it! [ al