i have ever had in my entire life. we can do this. you can do this. we can all do this together. (man) register today for the... because everyone deserves a lifetime. on the broadcast tonight. an aspirin a day that could help prevent and treat cancer. the new health research tonight that's being called a game changer. the earthquake in mexico tonight, the early reports of damage after a big hit there. final moments. there's news tonight about the last phone call in that florida shooting that has sparked national outrage, and now a federal investigation. and the enduring mystery. what happened to amelia earhart? tonight, one of the world's most powerful women joins in the search for one of the world's most famous women. "nightly news" begins now. captions paid for by nbc-universal television

good evening. we are going to begin here tonight with a story from the world of medicine that could end up affecting just about every american. this is a story about cancer, it's treatment and prevention, and this time it's a story about aspirin. it is without question the cheapest medication in the american household. its role in preventing heart disease and strokes is well documented. we call it the wonder drug. but this is about something else. it's new evidence tonight having to do with the role aspirin plays in cancer, specifically, helping to prevent and treat several different kinds of cancers. and we want to start off tonight with our chief medical editor, dr. nancy snyderman. >> reporter: like so many americans, dana garmani started taking an aspirin a day ten years ago to prevent heart disease. after being diagnosed and treated for colon cancer, his doctor told him to stay on it. >> my doctors in houston told me that aspirin therapy was something they thought would help prevent the recurrence of cancer.

so i've continued to take it for both reasons, the cancer and the heart. >> reporter: the medical journal says aspirin may have a new role in cancer prevention and treatment. consider the statistics. people who take aspirin had a 15% lower risk of dying from cancer. a 38% less chance of developing colorectal cancer. and aspirin may reduce the risk for cancers of the esophagus, stomach, breasts and lungs. taking aspirin regularly may also provide benefits even after diagnosis. aspirin users may have a 36% less chance having cancer spread. >> there's reason for hope that aspirin may have this an additional benefit in preventing cancer. but at the same time, we know it's not a panacea. >> reporter: doctors caution that aspirin still carries risks. it can cause stomach upset and bleeding. these new findings suggest the benefits of cancer prevention may outweigh those risks. and that has some doctors hopeful. >> my patients will often ask

me, is there something i can do to make my treatment better or more optimal? the answer oftentimes has been no. then something like this comes along, and we forget about aspirin. it can be incredibly helpful. >> reporter: doctors still insist you should watch what you eat, exercise and avoid smoking. but this little pill, an aspirin, that just costs pennies a day, this is one of those things you might just add to that list, brian. >> because it's ubiquitous and cheap, so many people are -- i think -- going to just want to run to this. who should be cautious, really? >> you know, no doctor's going to say everybody should be on it, but increasingly, doctors are encouraging folks. i think the subset of people who should be alarmed or hedge a little bit are people with any bleeding disorders, people who have had problems in the past. and certainly, you have to have your conversation with your doctor. the real advice today, especially remember, take the cheap stuff. the white crumbly aspirin you can see falling apart in the bottom, that's the stuff that dissolves easily, gets into your

stomach. and i think increasingly, we're going to find out that this humble little medicine is increasingly sophisticated and could be a lifesaver. >> already has the title the wonder drug. >> yes. >> thank you, nancy, as always. as we mentioned at the top of the broadcast, a large and long lasting earthquake struck the southern part of mexico today. this one measured a 7.4. it was centered near oaxaca, which is about 370 miles south acapulco. it was felt over a large area of real estate, including mexico city. a lot of people were scared, despite some heavy damage. there are no reports of early deaths as of yet. by the way, first daughter malia obama is in mexico on a school-sponsored service project in an area where the quake was felt. but the white house says she is safe and was never in danger. in texas, a tornado swept through devine, just outside san antonio last night. damaging homes but causing no

injuries. it was one of three twisters confirmed today by the national weather service. the same storm system brought hail, high winds, also flooding to parts of texas, oklahoma, kansas and arkansas got it pretty bad. flood watches and warnings are in effect over a wide area until thursday. 85 degrees in chicago by the way. now to the army staff sergeant accused of murdering 16 afghan civilians earlier this month. robert bales' lawyer spoke today after a long session with his new client. our report tonight from nbc's john yang. >> reporter: in 11 hours of conversations, staff sergeant robert bales told his defense attorney his memory of the night of the shootings is spotty. >> if you woke up and didn't realize what you had done last night, and people were telling you that you had done some really awful things and you had no memory of that, that kind of gives you an idea of what i'm talking about. >> reporter: john henry brown said he's seen this kind of thing before, in cases involving

head injuries, like the one bales suffered in iraq. he also questioned the strength of the military's case against his client. >> there's no forensic evidence, there's no medical examiner's evidence. there's no evidence about how many alleged victims or where those remains are. so, you know, it's fascinating from a defense lawyer's perspective. >> reporter: as the military's criminal investigation continues, the top u.s. commander in afghanistan announced an administrative investigation into bales' chain of command. >> it will look at the entire command and control process, how he was assigned, why he was assigned. >> reporter: outside seattle, movers emptied the house where bales lived with his wife and two small children, as more details emerged about his background. when he was a stockbroker, arbitrators ruled he and colleagues engaged in fraud, breach of fiduciary duty and unauthorized trading. he failed to pay a $1.2 million fine and was suspended from the

industry, but he had already enlisted in the army. brown didn't ask bales about it. as for the current case, brown says it's too early to tell how he'll defend bales. but made it clear, his client won't be the only one on trial. >> i think the war is on trial. i think the war should be on trial. and i'm hoping that the war will be on trial. >> reporter: brown says the army is trying to arrange a visit by bales' wife. they've only been able to speak once by phone since he was arrested, that's when he was being held in kuwait. they expect charges to be filed sometime this week. his attorney says he expects them to include murder, which carries the death penalty. brian? >> john yang, ft. leavenworth, kansas, tonight. thanks. as we mentioned, in illinois today, it's another summer like day in march. and it's another gop primary evening in our never ending political season. nbc's peter alexander is with the romney campaign on the trail

in schaumburg. peter, good evening. >> reporter: good evening to you, brian. mitt romney is expected to win here in illinois, a state with a lot of moderate republicans. to give you a sense of the dilemma facing republicans here and across the country in this drawn out republican primary campaign season, consider what with bob michaels, a retired veteran house leader from peoria, told me just this week. he's supporting romney, but he worries he's not a very exciting candidate who can rally republicans behind him. and he may be missing, what he calls that magical spark. romney still has been trying to cast himself this week as the presumptive nominee, focusing his attacks almost exclusively on the president. in fact, just yesterday at a speech at the university of chicago, where president obama taught, he attacked the president 12 times by name in less than 18 minutes. brian? >> peter alexander on the campaign trail tonight. peter, thanks. one issue that's been percolating through this presidential primary season, a push by some in the gop to limit

women's access to contraceptives and abortion, and it has some political observers wondering how it might affect the general election. our report from nbc's andrea mitchell. >> reporter: across the country, protests like this one in texas, against new state laws restricting access to contraception and other women's health care. >> maybe they don't want us to have freedom, but we're fighting back. >> it's a war against women's health. >> reporter: a fight college students took to mitt romney in peoria monday night. >> so you're all for like yeah freedom and all this stuff. >> absolutely. >> and yeah, like pursuit of happiness. you know what would make me happy? free birth control. >> if you're looking for free stuff, if you're looking for free stuff you don't have to pay for, vote for the other guy, that's what he's all about. okay? >> reporter: rick santorum said contraception is not okay, calling it a license to do things in a sexual realm that is counter to how things are supposed to be. in 39 states, legislators with similar views are rolling back access to contraception or abortion or considering proposals.

>> i think what we're seeing across the country, andrea, is so many legislatures that are now doing everything they can to shame women, and to make it more difficult for them to get health care. >> reporter: arizona's legislature would force women to prove to employers that they are using birth control for medical reasons not contraception. pennsylvania would require sonograms before abortions. a proposal the state's governor defended because, he said, it wouldn't be invasive. >> i don't know how you make anybody watch, okay? you just have to close your eyes. but as long as it's exterior, not interior. >> reporter: comments like his only added to the growing outrage. and the obama campaign is ready to take advantage, sending out campaign surrogates with starpower. >> i think the election is going to be about choice, and it's going to be pretty clear for women who's on their side regarding their health care issues. >> reporter: now, santorum's wife karen is trying to reassure women her husband won't impose his views on them. >> i think women have nothing to

fear, when it comes to contraceptives, he will do nothing on that issue. >> reporter: a gender war that could become a key battleground in the fall campaign. andrea mitchell, nbc news, washington. still ahead here tonight, the final phone call before the shooting death of that teenager in florida, and the young woman who was on the phone with him as the situation took a dangerous and terrible turn. and later -- she disappeared 75 years ago, trying to fly around the world. tonight, why hillary clinton has joined in the hunt for amelia earhart.

in florida tonight, demands for the arrest of a neighborhood watch volunteer who shot and killed an unarmed teenager last month, they are demands that are growing in the wake of revelations from a victim's girlfriend that she was on the phone with him as the incident happened. and the involvement of the justice department, the other new development in this case. nbc's ron allen with us tonight from sanford, florida. ron, good evening. >> reporter: good evening, brian. hundreds people are here inside and outside this church to confront local authorities and demand an arrest for the killing of trayvon martin. today in washington, the justice department said it would investigate the case. here in florida, the states attorney said he would let a grand jury decide what to do next. all that giving many here the

hope that justice will be done. the martin family laid out more proof that he was an innocent victim. his cell phone records indicate he was on the phone with a female friend at the time he met with zimmerman, and she heard what happened. >> she hears trayvon say, why are you following me? and then she hears at voice say, what are you doing around here? >> reporter: then she said she heard what sounded like an altercation. the defense says george zimmerman shot and killed trayvon martin in self-defense. a shooting with no racial overtones or hate crimes. but when zimmerman was calling police the night trayvon was killed he used a racial epithet. >> what entrance is he heading toward? >> the back entrance. [ bleep ] >> reporter: all of this is igniting more demands for an arrest. the victim's parents say their online petition has more than half a million signatures. for many here, the martin case is not an isolated incident. just last year, when a police officer's son assaulted a

homeless black man outside a bar, it took a month, and this video appearing on youtube, before charges were filed. in 2005, murder charges against two white security guards were dismissed after a black teen was shot dead. >> this is where it happened? >> yes, just about right here. >> reporter: in this quiet and comfortable community, where there had been a rash of burglaries, residents are still outraged by what they heard in zimmerman's neighborhood watch call to police. >> are you following him? >> yeah. >> okay, we don't need you to do that. >> he's not charles bronson, and this wasn't "death wish." this isn't a movie, it's an actual thing that's happened out here. i really hope the fbi can get to the bottom of it. ♪ >> reporter: but pastor valerie houston, a mother, says black parents have been warning their young sons to be careful for years. she's hopeful the martin family now gets some measure of justice. >> we don't feel like justice has been done. we do want an arrest. we want all the questions answered as much as possible. >> reporter: this is just one of several protests and town halls planned for this week. a lot of people are saying that

hearing those 911 calls, hearing the police tell zimmerman to back off, hearing martin's cries for help have turned up the intensity here. and again, zimmerman was nowhere to be found. brian? >> the attention finally coming down on this case. ron allen, thanks. a program note, trayvon martin's parents will be here in our new york studios tomorrow morning on "today" for an exclusive interview. up next here this evening, the queen's speech, marking a big milestone today in london.

big news in the fast food community tonight. there's been a change near the top. wendy's has bumped burger king from the number two spot, edging out burger king in sales for the first time since wendy's was founded by dave thomas back in 1969. mcdonald's, though, trumps both, and by a big margin. in london today, the queen celebrated her diamond jubilee. it's been 60 years since her coronation to the thrown

following the death her father. and today in a rare address to both houses of parliament, she paid tribute to the virtues of resilience, ingenuity and tolerance. and mentioned the only other british monarch to celebrate a diamond jubilee, queen victoria back in 1897. >> in an era where the regular worthy rhythm of life is less eye catching than doing something extraordinary, i'm reassured that i'm nearly the second sovereign to celebrate a diamond jubilee. >> the queen also had had kind words for her husband, prince phillip. she called him a constant strength and guide. in this country, the first lady revealed a little more about those secret shopping outings she's sometimes been able to take just to get out of the white house bubble. last night on the late show, she told david letterman about a woman she encountered recently at target. >> no one knew that was me. because a woman actually walked up to me, right? i was in the detergent aisle,

and she said. i kid you not, she said, "excuse me, i have to ask you something." and i thought, cover's blown. she said, "can you reach on that shelf and hand me the detergent?" i kid you not. >> the best part is, the woman not knowing who she had just spoken to, said to the very tall first lady, you didn't have to make it look so easy. it's going to soon be possible to fly from clinton to reagan and, if you wish, with continuing service to kennedy and bush. the little rock arkansas airport commission has unanimously voted to rename the airport there after bill and hillary clinton. the change will be effective once the faa signs off. just ahead tonight after the break, what happened to amelia earhart? a new clue pulls in one of the most famous women in the world.

heroes in the balcony, it's not every day you can look up from the floor of the nyse and see 30 recipients of the medal of honor ringing the closing bell, including our own military

affairs adviser, jack jacobs in the front row, left of center. we salute them all. and finally here tonight, she was a global celebrity and her disappearance has been one of the great enduring mysteries of the last 75 years. amelia earhart was fearless, a natural flyer, and way ahead of her time. on a july day in 1937 she disappeared while on approach to a remote pacific island. the search started an hour later and it hasn't stopped since. in fact, it's about to get a boost. our report tonight from chris jansing. ♪ >> amelia earhart, america's heroine, in the days when aviation meant adventure. >> reporter: amelia earhart was one of the most famous women alive in 1937. here with her husband before an attempt at an unprecedented around the world flight. >> how about taking me along? >> well, of course i think a great deal of you, but 180 pounds of gasoline on the flight perhaps might be a little more valuable. >> reporter: the world was captivated. >> miss earhart made a great hit

over there. >> reporter: on the final leg of her journey over the south pacific, her plane disappeared. >> we're still so intrigued and entranced by the story of this attractive modern woman who sets off on the flight of her dreams and never comes back. >> reporter: but now, new forensic imaging analysis of this grainy photo, taken just three months after earhart disappeared, may provide critical clues to earhart's fate. >> the photograph is consistent with the landing gear of a lockheed electra. >> reporter: in july, the international group for historic aircraft recovery will launch a deep water search for the plane, earhart's remains and the elusive answer to a cliffhanger so tantalizing, it brought out one of the most famous women of our day, secretary of state, hillary clinton. >> we too could use some of amelia's spirit. >> reporter: the common explanation for earhart's disappearance is simply that the plane ran out of gas and

crashed. but expedition leaders believe earhart may have survived that crash, a castaway on an island between hawaii and australia. finding the airplane could finally mean a conclusive answer. >> when she took off on that historic journey, she carried the aspirations of our entire country with her. >> reporter: and now a team of modern explorers will take with them the curiosity of generations. chris jansing, nbc news, new york. discuss and a bit of news to report to you before we go tonight. nbc news made a projection in tonight's illinois primary. we're projecting mitt romney the victor over rick santorum there. and further, when all the votes are counted it will be a sizable victory. it was an important pickup to mitt romney. he spent a lot of money in per suit of tonight's illinois victory. and with a race, this never ending gop primary campaign will go on from there. that is our broadcast for this

tuesday night. thanks for being here with us. we'll have more when we see you tomorrow night. good night. -- captions by vitac -- www.vitac.com good evening, everyone. thanks for joining us. i'm janelle wang in for jessica aguirre. >> and i'm raj mathai. we begin with developing news, the shake-up at city hall. san francisco sheriff ross mirkarimi said he will not step down. it's the latest chapter in a wild political scandal. jodi hernandez joinss