tonight on "nightline," glimmer of hope. after american exchange student amanda knox is convicted for a sex-fueled murder in italy, new dna analysis emerges that could set her free, after almost four years in jail. we talk to her parents and have the latest from overseas. human torpedos. it's sexy, fast and dangerous. and it's all the rage on this beach. free diving, taken to a new level. a race around and incredible underwater course. we channel our inner aquaman. and, retouched. glamour shots manipulated to make women look prettier, skinnier, sexier. but no the practice is coming under fire, as not only in bad taste, but bad for public health. >> announcer: from the global

resources of abc news, with terry moran, cynthia mcfadden and bill weir in new york city, this is "nightline," june 29th, 2011. >> good evening, i'm bill weir. it's been nearly four years since american exchange student amanda knox was arrested in italy and accused of killing her english roommate in a sexual encountetethat turned deadly violent. knox, along with her boyfriend at the time, was convicted in 2009, but today, the 23-year-old got new hope that she will not pass into middle age in a foreign prison. abc's elizabeth vargas has the story for our series, "crime and punishment." >> reporter: this was the scene when american college student amanda knox was convicted for violently killing her british roommate meredith kercher, while studying abroad. >> knox and her former boyfriend were found guilty.

>> sexually soughting and killllg miss kercher. >> reporter: fuhr chaos amid cheers and outrage in per reej ya, italy. a nightmare come true for knox's family. just an hour after hearing his daughter's 26-year prison sentence, knox's father curt and her sister deanna were overwhelmed. >> i thi i think those of us who have family members, who have children, couldn't help what it was like that moment, standing in that courtroom tonight and hearing that word, guilty. >> i collapsed shaking. >> it's not what anyone wants to experience. it's terrible. >> reporter: knox has lived in an italian prison since her arrest nearly four years ago. as has her then-boyfriend, who was also convicted. for the past six months, a new panel of italian judges and jurors are hearing knox's appeal, which she hopes will

overturn her conviction. and finally, today, a glimmer of hope for amanda and her family. two independent dna experts who have poured over key dna evidence in the case since february filed their 144-page review of the dna. crucial to knox's appeal. and their findings seem to support amanda's defense. the report states that dna traces on two key pieces of evidence were too tiny to be tested, and that proper procedures were not followed. the evidence in question, the victim's bra clasp that was said to contain dna of solleleto and a knife found with dna on it. knox's lawyers and family asked for an independent dna review during knox's trial. that request was denied. today's independent review even stated, quote, it cannot be

ruled out that the result obtained may stem from contamination. the reports confirm what american dna experts told us earlier this year, after reviewing the evidence. >> each time you handle something, even if you have glgles on, you are increasing the chances of contamination. if you're really being careful, you're changing gloves after each touch of a piece of evidence. clearly from the video, it doesn't seem they are doing that. they're wearing gloves, but touching multiple things. >> reporter: the news was huge, critical in amanda's chance for freedom. knox heard the news from a television in her cell. >> experts say the dna is potentially contaminated. that's a big step towards bringing her home. >> i w w thrilled. i was,ou know, worried for amanda and how she was hearing and how she was reacting.

>> reporter: amanda's mother got the news today in italy. >> i was able to speak to the priest in jail who was there when she heard the news. he said, you could see the light in her eyes and she could finally breathe for the first time in over three years. >> reporter: knox's defense also says a key in their appeal is that there is no dna at all from knox in the bedroom where the murder happened. nowhere in meredith's room where the murder took place and where her body was found is there a single fingerfrint from amanda, a singer piece of dna from amanda, a hair -- >> nothing. absolutely nothing. >> reporter: judy is a journalist who covered the case from the start. >> i was pretty positive when i started working on the amanda knox story that she was guilty. but as i examined the so-called evidence against her and as i examined the judge's words, particularly, i became convinced that she is not guilty. absolutely convinced. this was a rail road job.

>> reporter: but there is plenty of dna from this man. rudy guede, a local drifter, and the third person convicted for the murder of meredith kercher. guede's bloody hasn't print, seen here on the wall of the crime scene. his fingerprints on her bra. >> there is lots of dna and there are fingerprints from rudy. there is none from amanda knox. >> reporter: guede admitted himself he was in the cottage, but did not participate in the crime. this week, he took the stand, and toddress claims by follow inmate that he told them knox and sollecito were not in the house that night. he said that is not true. >> i was hoping rudy would own up to his responsibility and essentially tell the court that

amanda had nothing to do with it. >> reporter: ultimately, the truth may simply come down to science. >> i think the story of how this crime was committed doesn't fit the evidence collected. >> please, please, you guys. >> reporter: knox's family has defended her and visited her in prison since day one. this isn't going to be over any time soon. how do you continue on through -- >> you have to. you stay focused on amanda. and making sure that that light is there for her. and you just work through it ch. you just have to. you're not going to leave an innocent daughter in a foreign prison. >> reporter: for knox and her family, the emotional and financial toll, more than $1 million to date, are nearly too much to bear. can you really ever go back to life as it was, after what

you've been through? >> well, you know, none of us is ever really going to be the same, but we'll all make a new normal and just kind of go from there. >> reporter: i'm elizabeth vargas 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.

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[ male announcer ] nicorette mini goes wherever you go, to help make quitting suck less. >> announcer: "nightline" continues from new york city with bill weir. >> so, how long can you hold your breath under water? before you time yourself in the sink, you have to see this new sport. maybe the most dangerous in the

world. you've heard about guys who can reach enormous depths on a single breath in the search for a pure zen state. well, now, they are super charging that whole idea by holding propellerss between ther legs and racing. it's called formula three free diving and abc's matt gutman went to check it out. >> reporter: they go places humans shouldn't go. 60 feet under water, without oxyge oxygen. meet the fist generation of human or the bee dopes, hurtling through this race course, clinging to these 50-pound water scooters. >> free diving meets formula one meepts "top gun." >> three, two, one, go! >> reporter: this race takes free diving, diving as deep as you can on one breath, already one of the world's most deadliest sports, and turbo charges it. kurt crock, the sport's founder,

calls it formula three free diving. this is the most dangerous sport in the world? >> i would say so. >> reporter: "nightline" was here exclusively at the first and only event of its kind, a gathering of the best free divers in the world. five teams -- >> gold fusion! >> r rorter: vying for a $1,000 pot. except it's not about the money. but about adrenaline and pushing the limits of human capacity. you are taking to your body to the point where everything is contracting in your body -- >> why? >> reporter: yeah, why? >> i guess it's, you know, what can you do? what are we capable of? that's the draw for a lot of people. >> reporter: also a draw, this sport is sexy. and in its promo videos, crock is not ashamed to play it up. but i learned it is not all glamorous.

this i i not for the faint of heart. you have to go full monty. >> matt, we pee all the time in our wet suits. >> reporter: they jump in the water, and, like a school of fish, begin to inspect the race course. the rules today? well, they're still evolving. >> we decided no body contact, no physical action. >> reporter: that didn't quite work. and the equipment? still experimental. >> we lost a camera that went through the prop and broke the prop. in, a little training.can join crock worked on "the cove." trained david blaine for this lincoln center stunt, which included a seven-minute breath hold. he's trained six world record holders, tiger woods. >> catch your breath. >> reporter: and now, he's going to teach me how to hold my breath lonser than i ever felt possible.

these brth holds are called static about nia. and those jerking contractions, that's my body demanding to breathe. but that's the point. crock trains you to ignore it. after some instruction -- >> breathe, breathe, breathe. >> good job, man. all right. good, solid five minutes on the dot. that's a good, good, solid time. for someone who is a free diver already. so, that's a great time. that's an amazing time. >> reporter: that said, many push it all the way to blackout, causing drowning in great enough numbers to make free diving and spear fishing among the most dangerouousports in the world. back at the wreck, a handful watch the race. and as i learned, you canan get little too close to the action. team sililr won the event,

taking the $1,000 prize and a year's worth of bragging rights. but it doesn't end there. >> we can't envision what's going to happen in five years, i mean, some of the maneuvers and the modifications and all of those things will be hard to see where it's going to go. >> reporter: we were all victors of sorts. there's a tranquility down there. no cheering, no hot dogs. just the thump thump of your heart and the whir of propellers. that solitude becomes addictive. how many hours do you spend under water? >> well, in three years, over 230 hours free diving. >> reporter: you're a man-fish. >> well, sure. merman. >> reporter: and for a few blissful minutes, i got to play mer-man, too. i'm matt gutman, underwater in t the cayman islands.. take metamucil.

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the average fashion model is more than 20% underweight, according to a widely cited 2004 study. so, it's hard for normal sized folks to understand why magazines feel the need to photoshop models to make them look smaller. parents of girls have decried the practice for awhile, but now doctors are weighing in, and for

abc's stephanie sy, it's a sign of the times. >> reporter: never mind a little air brushing. photo editing software is wielded like a scalpel these days.. an already very thin kate middleton's waist was shaved to look smaller on this cover. and fresh off her pregnancy, jessica alba was given the photo-shaping treatment. today, the american medical association says images like these are dangerous, because they distort body image, especially for children. >> the only way they can achieve that body image is by photo editing. it's unreal ooisic for them to achieve that. >> reporter: their point is, while mirrors may not lie, photos can. it's almost a given that the advertisements in magazines are ma anyone lapted, photoshopped, air brushed, whatever you call it this is not reality. and thank goodness, because, if it were, this model's head would

be wider than her hips. ouch. many of these are apparent attempts of making alreadyy gorgeous people look even better. but look better in whose eyes? ask logan levkoff. >> we're not supposed to look like that. and the average person does not want a partner, a friend, or a sister or a parent who is unhealthy. >> reporter: sometimes it can all go very wrong. look. i have no rib cage. my goodness, my thighless legs are flexible. check me out. my shoulder has been dislocated. all that cutting, crotching and pasting has led so some gross examples of photoshop gone wrong. it's not just the fashion and beauty controversy that's creating controversy. newsweek's cover this week has given it a real image problem. the cover shows a magically resurrected princess diana as

she might look at 50. the actually photoshowed wrinkles onto her face and had her s sutting nest to a daughter-in-law she's never met. in another photo in "news week," an iphone has been photoshopped into her hand. to many, it's just plain weird. but at it worst, all this photoshop manipulation may be unhealthy. do you think the images are unhealthy? >> unfortunately, the answer to that is yes. these images can have a direct outcome and influence of what girls do, whether they diet, like their bodies, if they try to alter them or want to modify them. >> reporter: a picture may be worth a thousand words, but with photoshop, it may be worth 1,000 lives. for "nightline," i'm stephanie sy for new york. >> our thanks to stephanie for that. and thank you for watching abc news. we hope you'll check in on "good morning america." they have an exclusive interview with president bilin