>> the timing not so good on weekends. but spring-like weather in between. >> looks pretty good. "nbc nightly news" is coming up next. >> more local news at 6:00. hope you can join us. on this saturday night, where's the proof? the questions many are asking after president trump's explosive claim that former president obama tapped trump tower phones before the election. tonight, the extraordinary accusation and the obama response. getting physical. the new more comprehensive pat downs being introduced during airport security checks, what travellers could now face when they're asked to step aside. piece by piece, a rare look inside the national lab where crime scene evidence is dissected and murders can be solved. and the sweet spot, just why would this 13-year-old bake every day, making thousands of cupcakes? the answer nothing short of inspiring. "nightly news" begins now.

>> announcer: from nbc news world headquarters in new york, this is "nbc nightly news" with jose diaz-balart. good evening. it is unprecedented and unproven. president trump today accused president obama of using the federal government to tap his phones just before last year's elections. part of a flurry of early morning tweets. here you see some of them shifting the sung off of whether the trump campaign had any communication with the russian government. the president supporters are lauding his aggressive public attack. his critics say it's a concerning abuse of power. president obama spokesmen fired back it's unequivocally false. our casey hunt is in west palm beach tonight with president trump. >> reporter: without offering any evidence, president trump today making an explosive claim, that president obama tapped his phones before the election. >> this is what democracy looks like.

>> reporter: starting at 6:35 a.m. the president sent a string of five tweets, "terrible," he wrote. "just found out that obama had my wires tapped in trump tower just before the victory. nothing found. this is mccarthyism." comparing obama to nixon and watergate. he then hit the golf course. a senior u.s. official tells nbc news the president apparently didn't consult with people inside the u.s. government before he sent the tweets, that experts say could have profound implications. >> if the president's claims are correct it means that somebody in trump tower was involved in criminal activity or foreign espionage activity. that is a stunning admission. >> reporter: white house staff had been circulating this story from the right wing website once run by chief trump strategist steve bannon. by midday a spokesman for president obama released this statement, "neither president obama nor any white house official ever ordered surveillance on any u.s. citizen. any suggestion otherwise is simply false." at a town hall today, republican lindsey graham addressed the

tweets. >> i would be very worried if, in fact, the obama administration was able to obtain a warrant lawfully about trump campaign activity with foreign governments. >> but the claims could be a distraction, a frequent tactic of the president's. the accusations coming as the fbi investigates his campaign's contact with russians and pressure is mounting on capitol hill but with the country divided and protest both for and against the president today, americans are split on what it all means. >> it's a smoke screen. he's just trying to distract from the unbelievable amount of problems his administration is having. >> reporter: but his core supporters. >> what's going on today is just kind of a show of support for donald trump and his presidency. >> reporter: sticking with him all the way. president trump is sitting down to dinner tonight with embattled attorney general jeff sessions who recused himself from any investigation and the white house telling "nbc nightly news" the president plans to sign a new version of that travel ban

as soon as this week, setting the stage for more contentious fights. jose. >> case 'hunt thank you very much. and for more on the president's claims, let's turn to nbc senior legal correspondent ari melber. good to see you. u.s. officials tell nbc these claims by president trump about the president former president obama are baseless. that being said, what would it take legally to wire tap trump tower? >> there are two ways to do a tap in this situation. number one, a judge finds that there is evidence of crimes by some u.s. person and their being targeted or two, there was evidence of foreign espionage and the target was not the people in the united states but rather some people representing a foreign power abroad. >> so who could call for these taps? >> basically this would go through any normal prosecutial process and that means that a federal prosecutor is seeking them going before a judge or in the international context, going before the foreign surveillance court. >> so if there are legal wire taps of any of the trump associates, what would that

mean? >> that is the biggest question, right? if the president is correct, that there were lawfully ordered wire taps, that would actually be bad for trump or his associates because it would suggest that a judge at least found evidence to pursue whether that was for u.s. persons or an international context. the opposite would also be potentially be bad if the president made these claims without first verifying whether they're even true. >> ari melber good to see you. you'll be hearing much more about all of this on "meet the press." chuck "today's" guests will include senator schumer and marco rubio. many of us have experienced it getting patted down by an tsa officer. usually after setting off the electronic scanners. now the tsa will be making those pat downs more comprehensive under a new policy taking effect. we hear about it from nbc steve patterson. >> reporter: tonight air travellers may start feeling a difference in airport security lines. the tsa tightening rules on passenger pat downs. previously transportation security officials

used several types of pat downs usually after a person sets off the metal detecter alarm. now those options have been replaced with a universal procedure that's more comprehensive. >> from an operations perspective it's a little bit easier because everybody just has to learn one procedure, one technique and they don't have to try and make a judgment call as to which one to use. >> reporter: in a statement to nbc news the new procedure does not involve any different areas of the body than were screened in the previous standard pat down procedure. the tsa says pat downs will still be done by an officer of the same gender and it may still include inspection of sensitive areas such as breast, groin and the buttocks. >> this is not anything that's going to benefit security and all it does is turn the check point into a place of indecency. >> reporter: today travellers had mixed reactions. >> if it helps prevent something it's a good thing. >> if they do it when the police do, i think it will be invasive. >> reporter: the rule change

follows a 2015 homeland security study. tsa officers failed to detect smuggled weapons in 67 out of 70 times. 95% failure rate. a new procedure for an old problem. the balance of keeping the americans safe in a post 9/11 world. and that new procedure is not expected to slow down security traffic. travellers wade through those security lines for spring break, a ten year high for travel volume. >> thank you. a sad day in nashville, tennessee as a funeral was held for a young nurse who was stabbed to death four days ago. a manhunt intensified for the suspect. we get the latest. >> reporter: tonight no arrests as police continue their search for the killer who stabbed the gifted young nurse to death in nashville.

tennessee native tiffany ferguson worked in icu of this hospital where she was described as a rising star. a two hour drive from the crime scene, family and friends gather today to pay their final respects. tiffany's hometown dotted with teal ribbons, her favorite color, for her funeral. >> she just loved people. she was good to people. she was genuinely good to people. >> she put her all into her patient care -- she was there for them, not just physically -- physical care but emotional care too. >> reporter: early tuesday morning, security video shows a man police say was looking for unlocked cars near her home. before entering the apartment ferguson shared with friends through an unlocked front door. police believe he was confronting her and stabbing her multiple times. a search warrant reveals investigators found finger print and dna evidence at the scene, even tearing out pieces of carpet for tests. the police tonight promised to update a wary community when an arrest is made. >> we want to calm their fears. >> reporter: tonight, those who worked and

lived along ferguson hope a break in the case comes quickly, giving them the answers they are desperately waiting for. >> she needs justice. she was not only a great human being, she was a sister, she was a daughter. she was a friend. she was loved. >> reporter: and ferguson gave no indication to friends that she felt unsafe living here. in fact, she and her roommates had planned to renew their lease the very day she was killed. meanwhile residents plan to meet next week with police and a city councilman to discuss the case and safety going forward. >> thank you very much as we noted at the top of this broadcast, president trump is in florida this weekend at his mar-a-lago property in palm beach for the fourth time since he took office. it turns out the impact of these visits is being felt well beyond the walls of the so-called winter white house. we get that story from nbc's gabe gutierrez.

>> reporter: he used to be flying high, not any more. >> we're basically going broke. >> reporter: with president trump at his mar-a-lago resort tonight, this man's company southern helicopters is once again grounded. >> we were not expecting him to come down almost every weekend. >> reporter: the secret service restricting flights at the entire airport. on a typical weekend that president trump is in town all this will be shout down? >> correct. >> reporter: jonathan miller says the cost per weekend is $30,000 in lost business. >> and i don't know that my business can sustain heavy losses like that. >> reporter: local taxpayers are also getting hit. palm beach county paying $1.7 million so far for extra security. >> we've written a letter to the federal government asking for the reimbursement for the overtime for the sheriff and the impacts. but as of today we haven't heard back. >> reporter: as a candidate, mr. trump said he'd rarely leave the white house and blasted president obama for vacations costing taxpayers millions, but since his inauguration

president trump was spent four of the last five weekends at mar-a-lago. of course travels not unusual for the commander in chief. at this point in his first term, president obama was taking his third weekend getaway, one to chicago, two to camp david while the trump administration won't disclose the exact price tag, a conservative nonpartisan budget watchdog estimates it's almost $3 million so far in secret service and air force 1 costs alone. >> he should either travel his travel habits or find other ways to save money for the taxpayer and white house operation. >> reporter: on glitzy worth avenue with its luxury shops and upscale customers, president trump's visits are good for visit. >> i think there's a lot more people interested in coming to the avenue. >> reporter: the white house calls them working weekends. >> there's not rest at the southern white house. it's all work. >> reporter: but they're leaving some here without much work to do. nbc news, palm beach, florida. and once again this week the president took aim at china tieing it to the

loss of factories and jobs here in this country. the president's relationship with china is a work in progress. the country's are going in opposite directions on trade and that was an undercurrent today as the chinese leadership got underway. nbc reports from beijing. >> reporter: at china's biggest political show of the year, lawmakers agree with whatever leaders tell them but casting a long shadow how to deal with president trump who's unpredictability could impact china's economy, its leaders and stability. >> if president trump looks as if he is bullying or being unfair to president xi i think the chinese will have to react in strong ways. >> reporter: donald trump is up against the cult of xi jinping, near complete control, loyalty of government, military and the people. the most powerful leader in decades. but china is

undergoing a shift in how it sees its place in the world as president trump puts america first, china in many ways is choosing the opposite direction. like military spending. china said today it will ease up announcing the smallest spending increase in seven years. xi has also emerged as a cheerleader for globalization pushing the sort of trade deals and alliances that mr. trump wants to scrap. >> we've lost 60,000 factories since china joined the world trade organization in 2001. >> reporter: in a rare interview china's vice foreign minster says it's less about china leading the world than guiding it. >> because of the challenges that arise, i think china will have to counter them without hesitation. we never wanted to be imposed on and we will not impose on others. so i think we'll take our own path. >> reporter: the two presidents could meet soon, even for a

photo. if only to show there's room for common ground. janis frayer, "nbc nightly news," beijing. and there was new fallout today in the investigation of the poisoning of the half brother of north korea's leader. you'll recall that the killing happened in malaysia and today the malaysian government expelled north korea's ambassador after he credit siszed malaysia's handling of the investigation and refused to apologize. two women, one from vietnam, the other from indonesia, have been charged in the attack. still ahead tonight, we'll take a rare look inside the crime lab where no detail is too small when it comes to solving murders. also, the start of an arctic adventure what many say last's great race.

as chicago struggles to bring down its staggering murder rate, the city has become the country's number one user of a high tech crime lab that works to connect guns and bullets with the criminals who fired them. our justice correspondent pete williams got rare access inside one of these labs, run by the atf in maryland. >> reporter: from the streets of chicago they come pouring in, fragments of the rounds of ammunition recovered from crime scenes in a city where 4,300 people were shot last year with 762 murders. sometimes the only hard evidence is a spent bullet case found at the scene. chicago sends in a thousand a month. checking them for

valuable clues is the job of the atf national laboratory in maryland. chicago is also been atfs number one customer for tracing crime scene guns, nearly 6,000 in 2015. atf says 60% come from 14 other states illegally trafficked into the city. guns found at crime scenes can be sent here and test fired into a tank of water or at a firing range. the goal is to recover the cartridge case ejected when a gun is fired. every gun leaves distinctive marks, ballistic fingerprints from the firing pin, the cartridge ejector, and the back of the firing chamber a series of ridges and grooves. cartridge cases are digitally scanned and checked against atf's data base of millions of others looking for crime scenes for potential matches. >> these parallel lines here, they go all the way down. >> reporter: they seem to match from top to bottom. >> yes, they do. >> reporter: examiners use microscopes to

verify if there's actually a match. that tells police that the cartridge case recovered from the crime scene was fired from the same gun used to commit another crime of valuable investigative lead and if a criminal files or grinds off a gun's serial number, making it invisible, atf has ways to make it appear again. sharp and clear. >> our work here is getting criminals off the street. we're identifying a number of shootings that have taken place with the same firearm. looking for clues on a tiny piece of evidence that police say can help fight an epidemic of gun violence. pete williams, nbc news, beltsville, maryland. >> up next, the college all-american who ran his way to history today.

for 60 years, she was a fixture of stage, screen and television. actress miriam colon has died. she studied in the famed actor studio becoming its first puerto rican member. she had appearances on "bonanza," "alfred hitchcock presents" and "gunsmoke" and "nypd blue." just to name a few. in the movie "scarface" she was the mother of tony montana played by al pacino. 2015 she appeared in the tv series, "better call saul." miriam colon died yesterday in albuquerq albuquerque, new mexico. she was 80-year-old. it was a big day in alaska as the iditarod sled dog race

got under way today. the ceremonial start took place in anchorage. there you see about 2,000 dogs on 72 teams ran through the city. the official start takes place on monday in fairbanks. the teams will race nearly 1,000 miles to nome, alaska, it will take them between nine and 17 days in one of the world's most celebrated tests of endurance. another race to note tonight. this one measured in seconds in indianapolis. it looked like track but it was all about football. wide receiver john ross of the university of washington ran the 40-yard dash in a time of just 4.22 seconds, that's a lot faster than it takes me to read this script and tell you about it. a new nfl combined record as players compete in that event for top places in the nfl draft. when we come back, how one girl is inspiring america with the money she earns from making and selling cupcakes.

finally tonight we're going to meet a girl who was obsessed with cupcakes not just because they taste good but because cupcakes have become her currency to help children achieve a better life. here's how she's inspiring america. >> reporter: julia johnson is a girl on a mission. you're not looking at a recipe. >> this one i have memorized.

>> reporter: the 13-year-old bakes cupcakes seven days a week, before and after school, all from scratch, her own creations. why did you start baking cupcakes? what were you trying to raise money for? >> for my mission trip to ethiopia. we're going to orphanages and help the kids there. >> reporter: it's a cause close to her heart. two of her adopted siblings are from ethiopia. as word spread on facebook the orders poured in. >> she took the talent she had which was baking and she was passionate about it and she put it to work. >> reporter: jewel's julia's already made $10,000 cupcakes and raised enough money, not just for her trip, but enough to take her sister lucy to finally meet her birth mom. >> reporter: are you excited about going? >> yes. i just want them to be good and check on them. >> it's been a really fun to see everybody there. >> reporter: julia

plans to use some of the profits to buy livestock for people in ethiopia. you have a cupcakes call the starbucks cupcake frap chino. >> that's the one i'm going to make tonight. >> reporter: she's donating this batch to a local children's home, one of two places she visits every week, bringing a smile to these faces. >> take one, buddy. >> reporter: the kids count on her visits. >>or yo, mint chocolate chip, starbucks double chocolate chip frappuchino. it's definitely the sweetest part of their day. as for the future, julia's already got that figured out as well. >> part time baker. >> reporter: she plans to help as many kids as she can one cupcake at a time. tammy leitenor, nbc news, brandtwood, tennessee. and that's "nbc nightly news" for this saturday. on tomorrow's nightly news with kate snow, a look at how music is making a comeback in some schools with life changing results. thank you for the privilege of your time and good night.

right now at 6:00 a microclimate weather alert. we're tracking rain, thunder and cold weather about to hit the bay area. >> but first clashing over the commander in chief. a march of support for the president turns violent here in the bay area. the news at six starts right now. good evening everybody.

thank you for joining us. >> supporters of president trump are being met by counter protesters in berkeley that has led to punches being thrown and several arrests. we do have team coverage for you tonight. we start with nbc bay area's chuck coppola. >> reporter: good evening. martin luther king park behind minimum in berkeley is quiet at this hour but at one point a trump supporter who had been surrounded grabbed a bullhorn, flung it and let fists fly. this fight was one of more than a half dozen between trump supporters who were outnumbered by trump protesters. at least three people were blood i didn'ted and tried to clear pepper spray and smoke bombs from their eyes. trump supporters specifically chose berkeley to hold a march for trump event this afternoon. >> i'm just hoping there's not mass