courtroom bombshell. a shocking twist in a headline grabbing murder trial. and american accused and acquitted of killing her study abroad roommate. tonight, why amanda knox's nightmare is far from over. the celebrity fitness regiment that promises to give every joe six pack the abs to match the name. but are muscles like this really just a workout away? fitness missionaries say yes. and modern family? tonight, a culture phenomenon of acceptance. hollywood's profitable defense of the gay community. but how does america feel off the air? >> keep it right

>> from washington, this is "nightline" with terry moran. >> hello, everyone.

and thanks for joining us tonight. for amanda knox, 2011 was the year life began anew. the combination of four gruelling years spent locked away in an italian prison. following an appeals court ruling that freed her, knox returned to the u.s. relieved and thankful. but earlier today came an italian supreme court decision that all but ensures amanda knox's long fight for a return to normalcy will rage on. abc's neal karlinsky reports. >> reporter: even in a case filled with more twists and turns than a hollywood movie -- >> thank you for being there for me. >> reporter: the decision hit like an earthquake. at 2:00 a.m. back home in seattle, amanda knox, now a 25-year-old college student at the university of washington got the news that her life was about to take yet another painful

term. >> she's shocked, she's very sad. it's a nightmare and she's really strong and ready to fight again. we will continue tonig fight. >> reporter: it was italy's highest court, the supreme court that made the stunning reversal. amanda knox will face a new trial for murder, though the exact reasons remain unclear and won't be spelled out by the court for another three months. in a statement, knox said the court's decision was painful and completely unfounded and unfair. no matter what happens, my family and i will face this continuing legal battle as we always have -- confident in the truth and with our heads held high. >> there is no evidence. there was any evidence and there never will be any evidence. so they remained cautiously optimistic. they even upon this remand to the appellate court that the same result will occur. she will be determined to be not

guilty. >> reporter: one immediate question, how could this happen? after all, knox famously served four years in an italian prison for the murder of a college roommate, was freed on appeal in a dramatic and a motion charged hearing, then came home to seattle a year and a half ago to start a new life. complete with a reported $4 million book deal. >> i'm really overwhelmed right now. i was looking down from the airplane and it seemed like everything wasn't real. >> reporter: so how can a court in italy suddenly just change its mind? >> in this country, once there's a not guilty verdict, the case is over. but in italy, prosecutors can appeal. and they did appeal. and they won. and the high court effectively said try this case again. >> reporter: butt simply, the italian judicial system is very different than our own. even if she is convicted again, that can be appealed as well. >> she's worried.

she doesn't understand. the system here is different from america, and i know there's a lot of concern in america about what happened here. i think it's a fair system. we have to analyze why the court has decided. and after that, perhaps we will be in a position to say something more. >> reporter: knox came to perussia to study italian in 2007. >> reporter: knox and her former boyfriend were found guilty. >> found guilty of sexually assaulting and killing ms. kercher. >> it was just weeks after her arrival that meredith kercher was brutally killed. knox and her then boyfriend of just one week were arrested. overnight she became a murder suspect and international immediate obsession. in december 2009, they were convicted of murder after a dramatic year-long trial. knox was sentenced to 26 years in prison, sollecito, 25 years.

the verdict devastated her family, which made dozens of overseas trips and spent everything they had, more than $1 million fighting the charges. >> anger in how a judicial system could even come up with a verdict like this. >> this is completely unjust and i'm in complete shock. >> reporter: after 1,000 hours in court, knox pleaded her case in a last ditch appeal. i'm paying for my life for something i haven't done, she said. i'm not what they say i am. in a stunning move, the appeals court agreed. citing shoddy police work and a lack of forensic evidence and throwing out her conviction in an emotionally overwhelming verdict. >> what's important for me to say is just thank you to everyone who's believed in me,

who's depended me, who supported my family. >> reporter: since her return home, knox could be seen on the streets of seattle, getting coffee between creative writing classes. she has a boyfriend and lives in her own apartment. she has plans, too. amanda knox wants to make a living as a writer. but that will have to wait. her life yet again has been put on hold. >> no matter what happens in this case, i think it's very unlikely that amanda knox would be forced to go back to italy. >> reporter: amanda knox's chronicle of her ordeal will be published next month, long before the final chapter of her own real life drama is anywhere near finished. i'm neal karlinsky from "nightline." >> abc news will air her first interview with diane sawyer the

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seem to come from the rank and file of american exercisers. folks whose enthusiasm for this workout can seem to the uninitiated, a little wound up. at 6:00 a.m. on a saturday in downtown l.a., it looks like a come to jesus revival. >> what a great day! >> reporter: in spandex. think of them all as fitness missionaries, doing for the first time in public what they would normally do all by themselves in their living rooms at home. >> it's the ultimate 90-day home fitness program. >> a dvd program called p90x, now the workout of choice of hollywood a-listers. ashton kutcher, pink and usher. washington, too. p90x was practically a campaign issue last year after v.p. nominee paul ryan sang its praises to "politico."

>> pull utahs, sit-ups, lots of cardio, jump training. >> p90x has made tony horton a fitness celebrity. he's a hard body motivator, the tony robbins of the six pack. for three easy payments of $39.95, he would just change your life. a new now in 90 days. >> 60 pounds. >> 13? 75 pounds! >> it's like an auction. >> 50 pounds. you know what they all say? what do you guys always say? tony, thank you for changing my life. i didn't do the work. they did the work. all i did, a hammer doesn't build the house. >> reporter: the signature of the program is what p90xors refer to as their before and after. >> my proof of it, here's my before. and this is the after. real photos from real people, showing results. >> i'm definitely the before photo, by the way. >> i don't know about that.

>> reporter: even the ceo of the company has a before and after. >> the before and after photo is the visible proof. there's a trend of obesity in this country. i wish we could sell how good it feels to be healthy. but it doesn't move merchandise. it doesn't get people moving. the thing that gets them moving is the fact that they're going to look better that i know ear going to fit in those skinny jeans again. they're going to be able to go to the pool, take their shirt off and swim without hiding, without that embarrassment. >> then a they're not air brushed in any way? not photo shopped? >> never, no. >> reporter: it helped make beachbody.com a $400 million a year business. they have plenty of other workouts familiar to exercisers. >> turbo jam, turbo fire, p90 x. 10-minute trainers, thin thighs guaranteed. >> is there really a guarantee? >> absolutely.

>> reporter: but so far, p90x has the biggest cult following. did you know in life that you would end up being a guru? >> no, no. a guru is the last thing i wanted to be. i wanted to be brad pitt and jim carrey all wrapped in one. >> reporter: tony horton is the front man, but it turns out he's not even a certified trainer. horton tried to make a go at acting, playing a police detective in a soft core porn movie called "rebecca's secret." to earn extra money, he ended up helping other actors at the gym. instead of becoming a movie star, you ended up -- >> training them, yeah. >> reporter: that led to infomercials he was the guy in suzanne somers thigh master ad. >> want to tone your upper chest and arms? thigh masters will give you excellent results. >> reporter: now with p90 x, he's front and center. in millions of living rooms across the country. >> what tony is great at is taking this highly technical

functional fitness and presenting it in a way that have literally millions of people love and millions of people can do without getting injuried. >> reporter: p90x has been so successful, they've added a new line of shakes and nutritional supplements. >> cheers. >> thank you, sir. >> reporter: they're marketing a sequel called "insanity." that's taking off in a big way. >> insanity is the hardest program ever put on dvd. >> those guys on venice beach, right? >> no, this is more like functional fitness. the kind of bodies you saw in fight club. lean and ripped and tight. you know? this is cover of a magazine kind of shape. >> reporter: they're licensing p90x and insanity to gyms so you no longer have to do these workouts at home alone. and they're now enlisting the faithful to go out and recruit converts. that's what this weekend conference in l.a. was all about. teaching p90xors to make money

signing up new p90xors. forgive me, as somebody who hasn't done this yet, and i would like to try it, it seems a little culty. >> culty? how so? >> reporter: the people that are into it are so passionate about it. and, you know, what you're talking about is sort of not just a fitness program, but a life transformation. and then having the people that have gone through it go out and sell it. it just feels a little culty. is that unfair? >> i think it's a perspective that is cynical. i don't want to go to a gym, i want to be by myself and do a workout. that's not culty. >> they all work out naked. i've seen it. i sneak up at night. >> reporter: you would work out naked too if you already achieved your after. i'm david wright for "nightline" in los angeles. >> the extreme workout world. thanks for that. next up, from "glee" to "modern

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. the stories we see and hear on tv are more than entertainment. they're signs of a collective social consciousness, narratives that bring to life the changing tides we swim in every day, sometimes without even realizing it. this week, as the supreme court hears two cases involving gay rights, we can't help but notice the role hollywood may be playing in one of the most important social issues of the 21st century. it all happened so fast. as the great despite over gay marriage arrives at the supreme

court, the astonishing thing is how much the country has changed. >> you could hear it in the confidence and the voices of the gay couples who brought the big case. >> i believe in equality. i also believe in our judicial system and have great faith in it. but more than anything, i believe in love. >> something happened. >> the question, who's the big cheese you're having here for lunch? >> roger. >> roger the fairy? >> did you hear that, edith? do you know they're bringing around for lunch? >> reporter: it wasn't that long ago, bigotry against gay americans was open and accepted as "all in the family" dramatized and challenged. >> just because a guy is sensitive and he's an intellectual and he wears glasses, you make him out a queer. >> i never said a guy who wears glasses is a queer. a guy who wears glasses is queer. a guy who wears glasses is four eyes, a guy who is a fag is a

queer. >> will and grace, gray's anatomy, "glee" and "modern family." they all feature gay characters in lead roles. naturally. . >> mitchell's mother has a problem with me. >> are you guys together? >> of course not. he's gay. >> and she's married. >> you're married? >> you're gay? >> hello, how many straight guys do you know who wear vests? >> hollywood is also reflecting something deeper. our news poll shows 58% of americans now support gay marriage. in 2004, just 32% favored it. politicians know what that means. from president obama -- >> i think same-sex couples should be able to get married. >> to hillary clinton. >> i support marriage for lesbian and gay coup 8s. >> reporter: to ohio republican senator rob portman. >> i have believed that people ought to have the right to get

married. >> reporter: there's a stampede for support of gay marriage at the highest levels. big business supports it, too. >> my husband is getting me a drink right now. >> so is mine. . >> i think people started telling their stories. >> reporter: jeff and his partner paul brought the case in the supreme court. >> it's when we started talking to our families and we start talking to our friends and our neighbors and our co-workers. and people that we go to school with when people realize they have a connection to someone who's lgbt, they start to understand. >> reporter: rob reiner who played "meat head" on all in the family and is a leader for equal marriage right, he says even archie bunker might be persuadable. >> i would think archie would be convinced if one of his friends or his daughter -- not the daughter i was married to, but if he had a child that was gay, i think he might be convinced.

>> reporter: in the end, it's about families, about all those conversations, about the fact that through them gay americans are really liberating themselves. >> and we are an american family. [ applause ] the power of stories, personal and pop culture. homosexuality has become part of the american mainstream culture. more americans in favor of equalizing gay marriage. but are those two trends linked? what do you think? do more americans support gay rights because of what they see on tv? weigh in on the "nightline" facebook page or tweet us at nightline or @terrymoran. check in for "good morning america" they're working while you're sleeping and we are always online at abcnews.com. see you here tomorrow.