this is "nightline." tonight, breaking his silence. blade runner oscar pistorius on trial for the murder of his girlfriend finally takes the stand. >> i have terrible nightmares. >> but is it sorrow or strategy? body war battle. on one side the fit mom of three who asks what's your excuse? >> don't worry, i'm not apologizing. >> on the other, mothers who say she's fat-shaming. now we bring them face to face. and royal welcome. prince william and duchess kate on a tour down under. but it may be george everyone's swooning over on his first official business trip. but first, the "nightline" top five starts right now.

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salesperson #2: actually, we're throwing in a $1,000 fuel reward card. we've never done that. that's why there's never been a better time to buy a passat tdi clean diesel. husband: so it's like two deals in one? salesperson #2: exactly. avo: during the first ever volkswagen tdi clean diesel event, get a great deal on a passat tdi, that gets up to 795 highway miles per tank. and get a $1,000 fuel reward card. it's like two deals in one. hurry in and get a $1,000 fuel reward card and 0.9% apr for 60 months on tdi models. good evening and thanks for joining us. paralympian oscar pistorius has been in court for over a month without speaking publicly. until now. the athlete once famously known as the blade runner finally taking the stand today in his murder trial. he admits he shot and killed his

girlfriend, reeva steenkamp. but how did it happen? and why is he apologizing now? abc's matt gutman is in south africa with this report from inside the courtroom. >> reporter: it was a moment anticipated for 14 months. oscar pistorius solemnly making his way to the witness stand, breaking his silence with a sob-filled apology to the woman he loved. the woman he's charged with murdering. >> there hasn't been a moment since this tragedy happened that i haven't thought about your family. i was simply trying to protect reeva. >> reporter: the blade runner once indomitable on the track. now his voice quivering, barely audible. >> i can promise you that when she went to bed that night she felt loved. >> reporter: after pistorius made his way to the witness stand he walked right here and addressed reeva steenkamp's family. the defense would not allow him to be videotaped so it was audio only. but here in court we could see

his lip quivering as he tried to talk to them. we could tell he hadn't slept in days, his eyes sunken and dark. and for the rest of his nearly three-hour testimony he sat here like this, hunched over. steenkamp's mother sat stone-faced, seemingly unmoved. unlike others in the courtroom, who swept. legal analysts say his testimony is the hinge on which this trial to could turn. pistorius admitted to shooting reeva through the closed door of his bathroom at home on valentine's day last year. pleading not guilty, he claimed he mistook the model and reality star for an intruder. >> we're only interested in weth in h whether in his own mind he thought he was acting unlaflly in that moment. >> reporter: and what would unfold for the next three hours in a stuffy pretoria courtroom would essentially be the blade runner's autobiography, perhaps an attempt to humanize him in the eyes of the world. and the judge who will decide his fate. starting with his traumatic last year. >> do you have difficulty in sleeping? >> i'm scared to sleep. i have terrible nightmares.

about things that happened that night. i wake up and i can smell the blood. and i wake up to being terrified. >> his defense attorney asking him to describe his descent into paranoia. >> i've got a security guard that stands outside of my front door at night. >> reporter: it is a trauma so thorough, said the broken man testifying, that after living through the ghastly tableau shown in crime scene photos in court, he's on medication for depression and throughout still professing his love for reeva. >> i was kind of taken aback by her and just bowled over by how much i fell for her. >> reporter: he says he always kept his gun close, under his bed, he says to protect his beloved girlfriend and himself. pistorius grew one a healthy fear of the outside world. his mother divorced from his father when he was just 6 years old, kept a pistol beneath her pillow. her fear of south africa's rampant crime would become his. >> living with my mother we were

broken into on several occasions. my father has been hijacked twice. my brother was in an intense hijacking. >> have you ever been a victim to crime? >> yes, i have. >> reporter: and that sense of insecurity, that fear of crime is shared by nearly all south africans. after all, the incidence of burglary, home invasion, rape, murder, so much higher here than in the u.s. and the paralympic champ said he felt it more keenly than others, especially when he wasn't wearing his prosthetic legs. >> it just throws my weight off completely. my dog could knock me over without my process tet uk legs on. >> reporter: pistorius appears to be a shell of the fearless olympian he was a year ago. his former agent was there for the good times. >> how high was he flying before the shooting? >> he was an icon. the world loved him. he was unbelievable. >> reporter: he couldn't believe the transformation when he saw pistorius in the weeks before the trial. >> i didn't recognize him. and he came, he said can i have

a hug. and he gave me a hug. he was shaking. and he said, not too many people love me anymore. >> reporter: it is this portrait of a man crippled by guilt and depression who'd always felt vulnerable, who felt the need to arm himself against the outside world, which could actually be the key to his defense. >> he'll of course raise the fact that he is disabled, that he has a heightened sense of vulnerability compared to other people in the same position. >> reporter: his story winding down, pistorius seemed to sink in his chair. >> did you sleep last night? >> no, sir. >> reporter: his attorney called for an adjournment for the day, and the judge assented. >> well, he does look exhausted. he does sound exhausted. >> reporter: walking out of court, the once invincible olympian looked shattered. but he returns to this courtroom tomorrow with the final chapter of his tale left to tell, a valentine's day tragedy that ends with his love dead in his arms, a murder charge against him, and a single question. why did he pull that trigger?

i'm matt gutman for "nightline" in pretoria, south africa. >> of course the key will be how does he hold up on cross-examination? thanks, matt. next, from kesha to mindy kaling, body acceptance is having a hollywood moment. but not everybody thinks that's a good thing. why moms are taking sides in the body wars. coming up next. this is jim. a man who doesn't stand still. but jim has afib, atrial fibrillation, an irregular heartbeat not caused by a heart valve problem. that puts jim at a greater risk of stroke. for years, jim's medicine tied him to a monthly trip to the clinic to get his blood tested. but now, with once-a-day xarelto jim's on the move. jim's doctor recommended xarelto. like warfarin, xarelto is proven effective to reduce afib-related stroke risk. but xarelto is the first and only once-a-day prescription blood thinner for patients with afib not caused by a heart valve problem that doesn't require routine blood monitoring. so jim's not tied to that monitoring routine.

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at kaiser permanente we've reduced serious heart attacks by 62%, which makes days with grandpa jack 100% more possible. join us at kp.org and thrive. you're about to meet the fit mom. some see her toned body and everything it stands for as an inspiration to shape up. but critics believe she's condescending and out of touch. and when she asked "what's your

excuse," thousands of women fired back with very real answers. so we thought we'd bring them together to square off in person. here's abc's paula farris. >> reporter: from the runway to the red carpet, body fat is so in vogue. girls willing to bear bare it all like lena dunham. >> we were saying how much we loved your bikini. >> i heard you laughing about it. >> joan rivers. >> you're sending the message it's okay, stay fat, gets diabetes. >> reporter: and mindy kaling's laughing it all off. >> mindy let herself go and let herself be a fat sea monster. >> reporter: but fat shaming can also be serious. "die quuyoung" singer kesha say it's what led her to rehab for an eating disorder. ♪ tonight we're going to die young ♪

and now the fight has spilled from the front pages to our home pages. when this mom posted "what's your excuse," it sparked reactions from tens of thousands of women. >> wow, this woman is so inspiring. >> she should be ashamed for fat-shaming other mothers. >> if this is fat shaming shame away, my baby weight is coming off. >> reporter: and that was excuse enough for us to meet the fit mom. maria kang, mother of three, fitness fanatic, and accidental instigator of the latest battle of the body wars. >> so we're going to do a little bit of legs. >> i've heard that i'm a bad mom. i've heard that i'm a fat shamer and a bully already. i'm just saying what's your excuse for not making health a priority? >> show america how tough moms are. go. >> reporter: maria has turned her controversial tag line into a movement. >> i don't think asking moms to work out is judgmental because everyone should find time in their day at least 20 minutes. >> reporter: in just six months no excuse moxb]lubs popped up

but her unrelenting no excuse refrain is what drove a soft-spoken kansas city mom to post this. >> you don't know till you've worked a schedule like this. >> reporter: sarah mabin juggles a job as an overnight security guard and her day job caring for her two kids. so she routinely does 36-hour stretches with no sleep. outraged by fit mom's post, it was sarah and some friends who launched a "we don't need an excuse" counteroffensive. >> this makes me feel shamed. this makes me feel like i'm supposed to live up to a standard. >> reporter: and now, after months of battling it out, they've asked fit mom to come to kansas city and challenge her to walk in their shoes for one day. >> you know what? this is a tough life. >> reporter: i wonder why they chose me for this assignment. >> i've been on maternity leave for about 2 1/2 months. i feel the pressure to get back in shape. in fact, i'm wearing a compression tank to suck it all

in. first we meet up with maria in california who assures us she doesn't work out all day. she runs a chain of homes for the elderly, chases her three boys around, and even does a regular local news segment. >> you know, sleep is so important. >> reporter: next up, sarah's home turf, where the moms will take it off the blog and to the kitchen table. >> she's pretty unapologetic. so i feel like it's going to go in one ear and out the other. >> hello. >> reporter: so she's not outgunned, maria and christie, the leader of cancel city's no excuse moms club as a backup. >> i didn't want to come into this situation and be by myself and feel like i'm being ambushed by these moms. can we hold hands? >> reporter: with so much pent up, i don't need to do much. >> you don't think that in any sense maria's fat-shaming? >> i don't. at all.

>> do you? >> yes. part of the reason i think that we have so many body issues, particularly in this country, is because we're -- no. regardless of whether you're intending shame, when people feel shamed they feel powerless. >> saying that somebody needs an excuse is implying they are at fault for someone. >> i don't think anyone should look like me. >> you don't have those disclaimers on that photo. and you say you're not responsible for the thoughts that are in other people's minds. but that's very similar to a celebrity saying i'm not a role model for children. but you are. you plummeted yourself into this -- >> oh, don't worry, i'm -- >> i always tell people that any mom's photo could have been viral but mine did and they messed with the wrong mom because i have something to say. sure, i attracted you with my face, with my abs, with that caption. but when it comes out of my mouth about -- >> i love you but you're on the wrong track. >> that's fine. but i'm attracting other people.

>> the difference between our two moms seems even greater. >> good morning, kansas city. it's kind of early. 20 minutes before a very long day. >> i didn't get the impression that she is willing to see any other side but hers. >> sometimes people vilify me to the point where they think i don't know what it means to be busy. and i actually do know a lot about that. >> reporter: three adults, one child, two car seats to install. go. let's see how fast you can get in the car. >> reporter: what better way to bring people together than a day in the family mini van? and we're off to experience a day in the life of sarah. which means a lot of time in here. >> and i just feel like oh, come

on, i'm a mom. and i feel like you took my mom badge away from me. >> i am so sorry that i made you feel that way. >> reporter: our first stop, diane's home schooling group. >> where does the rain come from? >> the sky. >> the sky? >> the clouds. >> reporter: sarah contributes her time here a few times a week. >> i would never, ever say fitness is a bad thing or obesity is a good thing. you have to determine what works for each person. i have a 36-hour day every week. >> reporter: because of his special needs, zaya is enrolled in activities all over town, and it's here maria thinks she sees a clear window of opportunity. >> run around the block for a good half hour. it's an hour class. you can always incorporate fitness. >> i do not have any kind of set exercise routine. i'll walk around the field. >> that's awesome, actually. >> reporter: for maria being a

good mom means taking care of yourself. which is why she started the no excuse mom club. >> let's do this, baby. >> reporter: she invited me, sarah, and diana to the kansas city chapter so we could see what the movement is really all about. >> with the baby? >> reporter: but sarah's soon on the sidelines, unable to join in. >> we spent a lot of time in the car today. do you think that maybe you could carve some time out for yourself? >> well, it depends on what you're going to define as time for myself. if i took actual time to sit down and exercise, that would seem like work to me. >> reporter: diana and sarah will say she just didn't get our point. but so many people are misinterpreting the message. is it worth it? >> i think that the majority of people get the message and the small percentage that don't, i

don't focus on that. >> you spent the last 24 hours with diana and sarah. >> mm-hmm. >> what did you learn? >> i'm absolutely involved with sarah and her life and especially her kids. >> i think we're on very different paths in our lives, and i don't see them intersecting anytime in the near future. but i have a very deep respect for what she's done. >> reporter: for "nightline" i'm paula faris in cancel city. . next, it's hard to steal the spotlight from flawless kate middleton. but boy george, the royal baby, not the '80s icon, comes close. the royal family's new zealand adventure, coming up. you've reached the age where you know how things work. this is the age of knowing what needs to be done. so why let erectile dysfunction get in your way? talk to your doctor about viagra. 20 million men already have.

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prince george is only eight months old, but he's already crossing enviable items off his bucket list. traveling to another continent on a private plane, check. bringing a staff of nearly a dozen personal assistants and nannies, check. stealing the spotlight from an international icon, check. abc's cecilia vega's in new zealand with the boy who will be king.

>> reporter: the pomp and circumstance fit for a king. the duke and duchess receiving a ceremonial greeting from new zealand's indigenous people. traditional nose kisses known here as hongi. and for the world's most buttoned-up xushlgs a cheeky welcome from maori warriors wearing, well, not very much at all. on the first day of this royal tour down under style it is kate's style taking center stage. decked out in a diamond broach on loan from the queen and looking regal in red, for royal watchers the comparisons to a certain princess's 1984 trip down under were immediate. >> one of the things that kate always has to face is she's going to be compared to diana even though she is a different person altogether. it's an inevitable comparison. >> reporter: but only one person could manage to steal the royal

thunder from this power couple. prince george in all his royal cuteness on his first official tour of duty. we rarely see him until now. there was that brief appearance after his birth, a photo here and there, but with all this royal chubbiness now on full display the world swooned. >> so there they are. they've just touched down. you see prince george, will, kate, the baby looking adorable. this is the closest i've ever been to a member of the royal family. this is really exciting. the royal visit begins. >> reporter: and the man who will one day be king resigned to carrying his son's royal kangaroo backpack. but william doesn't have to do all the heavy lifting. part of the entourage, a royal nanny. >> it happened to the queen with charles and diana and now it's happening a little bit with prince william because in a way he's been outshone not only by his wife but his baby son. >> reporter: during their three weeks in new zealand and australia the duke and duchess

will compete in their own america's cup races and visit christchurch, devastated by an earthquake three years ago. it is a tour designed to replicate william's very first trip to new zealand. but by george, this time there's a new baby in town. for "nightline" i'm cecilia vega in wellington, new zealand. >> if you're going to be a baby, that's the life to have. thanks for watching abc news. i'll see you on "good morning america" tomorrow and as always, we're online at abcnews.com. good night. >> every day more americans