By Rayner Ramirez, NBC News
and Adam Yamaguchi, Current TV on assignment for Rock Center

California's San Joaquin Valley is one of the most productive agricultural regions in the country. It is also where, among the fresh fruits and vegetables, an estimated half-a-million plants of marijuana are growing openly, some allegedly being sold for non-medicinal purposes.

"In the last two years, we've seen large-scale commercial farming operations of marijuana and explosions of backyard marijuana grows," said Lieutenant Rick Ko of the Fresno County Sheriff's Office. Ko says the spike in cannabis cultivation is a result of California's booming medical marijuana trade.

California was the first state to legalize medical marijuana almost 16 years ago to help people manage the nausea and pain associated with serious illnesses such as cancer and HIV.

Law enforcement authorities say traffickers are hiding behind California's medical marijuana laws and distributing the drug illegally. Although medical marijuana is prohibited under federal law, 16 states and the District of Columbia have legalized use and enforcement of federal law is often limited to the worst offenders.

In California, Lt. Ko's team is attempting to limit the abuse of state and local medical marijuana regulations.

"We're looking for the people that are diverting medical marijuana from legitimate uses to either organized crime or profiteering activities," Ko said.

Some patients in California are getting doctors' recommendations to grow up to 99 plants of medical marijuana.

Federal sentencing guidelines are stiff for those caught growing more than 100 plants. However, Lt. Ko says even the lower amount is more than any single patient could ever need for personal use. Cannabis plants cultivated in the San Joaquin Valley can grow up to 18 feet high and yield up to three pounds of medical grade marijuana.

"Let's just take a conservative estimate of a pound per plant. And if you have 99 pounds then you are looking at over 89,000 doses in a year," Ko said.  "So you would have to smoke a joint every six minutes of every hour of every day for a year to use the 99 plants."

Rock Center

Slightly more than half of all people who took Rock Center's mock police photo lineup test were able to identify the correct suspect.

In early April, correspondent Josh Mankiewicz reported on new challenges to the way photo lineups are administered by law enforcement agencies after a series of wrongful convictions were identified. Viewers were then asked to take part in an unscientific test by watching a video of a mock crime taking place and then trying to identify the correct person seen in the video out of six fictional suspects.

Out of 2,499 responses since the Rock Center report was broadcast, 1,347 were correct -- 54 percent -- meaning 46 percent of test takers selected the wrong suspect from the mock police photo lineup.

Rock Center

Benjamin Kieffer started riding a unicycle in 1990 when he signed up for circus school, but now the 30-year-old rides his unicycle to work every day in midtown Manhattan. Kieffer tells Rock Center his commute is the part of the day he enjoys the most. 

Rock Center

Brandi Chastain, the star soccer player who helped the United States win a World Cup, is on a mission to get out a message to young girls playing soccer: the best way to avoid concussions is to sharpen their skills.

A growing number of girls are getting injured from concussions on the soccer field. Some experts have questioned whether the act of heading – when players attempt to use their foreheads to direct the ball – should be removed from youth soccer. Chastain strongly objects to that idea.

“It’s a part of the game and I think it’s an important part and I think it’s a beautiful part of the game, to be honest with you,” she told Rock Center's Kate Snow.  “I would never want to see that go away, but there’s a right way to do it. There’s a protective way to do it.”

Chastain said that along with learning how to properly head a ball, girls need to learn how to create a protective space around their bodies when they play soccer.  In this online exclusive, Chastain demonstrates techniques that can keep young girls safe on the field.

Click here for more of Kate Snow's reporting on the growing concussion crisis in girls' soccer.

By Kate Snow, Sarah Koch, Deirdre Cohen and Jessica Hopper

Rock Center

Fifteen-year-old Allison Kasacavage, once a rising soccer star in Pennsylvania, is slowly recovering after suffering debilitating concussions while playing the game she loved.

“It’s almost like I need a sign on my back saying, ‘My head is broken.’ And you can’t see it. It’s like not visible and it’s like not many people understand, “said Allison in an interview with Rock Center’s Kate Snow.

Allison, who lives with her family in Chester Springs, Pa., has had at least five concussions.  She is only able to attend school four hours a day.  Her room is lit with soft blue light to ease her headaches and her family now eats dinner by candlelight. 

She is one of hundreds of girls across America each year who suffer concussions while playing soccer. 

“People who think of concussions as only being present mostly in guys and mostly in the sport of football are just plain wrong,” said Dr. Bob Cantu, who is chairman of the surgery division and the director of sports medicine at Emerson Hospital in Concord, Mass. “Soccer is right at the top of the list for girls.” 

With the steady popularity of youth soccer, more girls are playing the game than ever before.  Girls make up 48 percent of the more than 3 million kids registered in US Youth Soccer leagues.

Cantu said that the country is in the midst of “a concussion crisis” and that studies show girls are reporting nearly twice as many concussions as boys in the sports they both play.

‘Concussion Crisis’ impacting girls’ soccer

The number of girls suffering concussions in soccer accounts for the second largest amount of all concussions reported by young athletes, according to the American Journal of Sports Medicine.  (Football tops the list.)

“What’s happening in this country is an epidemic of concussions, number one, and the realization that many of these individuals are going to go on to post-concussion syndrome, which can alter their ability to function at a high level for the rest of their lives,” Dr. Cantu said. 

Allison still remembers when she suffered her first serious concussion in October 2008.  It came when she collided with another player on the field. 

“When I like got up, my head was like pounding,” Allison said. “There was, like, a pulse in my head. It was like the strangest thing.  There was a heartbeat in my head and I had no idea what it was and why it was there.  I have never felt that before and I was just so confused,” she said.

Click here for more on concussion symptoms

By Jenny Dubin and Ronnie Polidoro
Rock Center

Neville Bardos, the U.S. Equestrian Federation International Horse of the Year, is gearing up for a potential spot on the U.S. Olympic team, a remarkable feat considering less than a year ago the champion horse was fighting for his life after surviving a deadly fire.

“Neville was the highest-placed American horse at the World Championships two years ago,” said Boyd Martin, the horse’s trainer.  But after a fire broke out in Neville’s stable, the 12-year-old chestnut thoroughbred horse with a white muzzle was unrecognizable when he turned black from the smoke and ash.  “The only thing you could see was Neville's two little eyes,” Martin said.

May 30, 2011

The fire happened at night last Memorial Day in a barn which housed 11 horses.  “I remember driving out there and there was just this massive yellow glow in the sky," Martin told Rock Center’s Harry Smith in an interview airing Wednesday, May 9.

“I thought to myself, ‘you know, this is real bad and my life's about to change,’” said Martin, who purchased Neville after he graduated from high school in Australia.

Neville was destined for the slaughterhouse but Martin sensed he was a champion-caliber horse.  The two placed 1st at the Melbourne CCI in 2006, 1st at the Fairhill CCI in 2009, and placed 4th at Kentucky CCI in 2010.

But disaster loomed at the True Prospect Farm in West Grove, PA.  Martin fought his way past the firefighters and raced into the barn.  Through a cloud of heavy smoke, Martin says he found a stable door and remembered hearing a gurgling noise.

Rock Center

In part two of this Hidden Planet episode, Inside the Pharoah's Secret Tunnels, Richard Engel journeys into the Great Pyramid of Giza in Egypt, the oldest of the seven wonders of the ancient world.

The pyramid's construction began in 2589 B.C., shortly after the 20-year-old Pharaoh Cheops ascended to the throne. Cheops' burial place turned out to be the biggest one in history.

Engel climbs through the hidden chambers and passageways of the ancient pyramid, revealing secrets about the largest pyramid of the Giza Necropolis and the pharoah it was constructed for.

Editor's note: New editions of Richard Engel's 'Hidden Planet' premiere monthly on the Rock Center iPad app. Download the app here.

Rock Center

Neville Bardos is a horse that has cheated death not once, but twice. The racehorse was destined for the slaughterhouse until his Australian-turned-American trainer, Boyd Martin, rescued him at the age of three. London 2012 marks the 100th anniversary of equestrian events at the Olympics and the pair are strong contenders to make the United States team. But no one would have believed this possible just a year ago.

Click here to watch Harry Smith's full report, 'Horse Power,' from NBC's Rock Center with Brian Williams.

ONLINE EXCLUSIVE: Nearly a year after Osama bin Laden was killed by U.S. forces, Rock Center with Brian Williams received unprecedented access inside the White House Situation Room. Brian Williams gives a guided tour inside the room where no network television cameras have gone before.

Click here to watch the hour-long Rock Center special: Inside the Situation Room

By Jessica Hopper, Subrata De and Tim Uehlinger
Rock Center

President Barack Obama describes the killing of Osama bin Laden as the “most important single day” of his presidency and said that the decision to carry out the raid was one that he had to ultimately make alone.

“I did choose the risk,” the president said in an exclusive interview with Rock Center Anchor and Managing Editor Brian Williams. “The reason I was willing to make that decision of sending in our SEALs to try to capture or kill bin Laden rather than to take some other options was ultimately because I had 100 percent faith in the Navy SEALs themselves.”

A year after the May 1, 2011, raid on bin Laden’s compound, Obama and several of the advisers who helped plan the operation, known as “Operation Neptune’s Spear,” spoke exclusively to NBC News, reflecting on the tense months spent planning and debating the feasibility of this daring raid. The interviews occurred before the president made an unannounced visit to Kabul on Tuesday, where he and President Hamid Karzai signed an agreement on the future of U.S. involvement in Afghanistan.

“This had to be such a close-held operation,” the president said. “There were only a handful of staff in the White House who knew about this.”

The president did not share news of the mission’s launch with his staff, or with the first lady.

“Even a breath of this in the press could have chased bin Laden away,” Obama said. “We didn't know at that point whether there might be underground tunnels coming out of that compound that would allow him to escape.”

The killing of the 9/11 mastermind had been years in the making, a mission that Obama’s two predecessors had been unable accomplish. President Bill Clinton fired 75 cruise missiles trying to kill bin Laden while President George W. Bush was frustrated by the al-Qaeda leader’s ability to evade capture.

Rock Center

Nearly a year after Osama bin Laden was killed by U.S. forces in Abbottabad, Pakistan, President Barack Obama, Admiral Mike Mullen, and Secretary of State Hillary Clinton spoke exclusively to NBC's Brian Williams. Pres. Obama reflected on the raid from the White House Situation Room, describing the tense moments as "the longest 40 minutes of my life."

Editor's note: Click here to watch the special edition of Rock Center with Brian Williams, 'Inside the Situation Room,' that aired Wednesday, May 2 on NBC.

Rock Center and Associated Press reporting

One World Trade Center, the giant monolith being built to replace the twin towers destroyed in the Sept. 11 attacks, will lay claim to the title of New York City's tallest skyscraper on Monday. Workers will erect steel columns that will make its unfinished skeleton a little over 1,250 feet high, just enough to peak over the roof of the observation deck on the Empire State Building.

Explore a panoramic image of New York City from the 69th floor of One World Trade Center

The milestone is a preliminary one. Workers are still adding floors to the building once referred to as the "Freedom Tower" and it isn't expected to reach its full height for at least another year, at which point it is likely to be declared the tallest building in the U.S., and third tallest in the world.

NBC's Harry Smith toured One World Trade Center and reported on the tower's construction progress last month for Rock Center with Brian Williams. At the time, iron worker Kevin Murphy told Smith, “In the next couple of weeks, we’re there.  That’s going to be another big, you know, special day.  Pretty much from here on up, everything’s special, you know?”

Nearly a year after Osama bin Laden was killed by U.S. forces, President Barack Obama described the tense moments spent watching the raid from the White House Situation Room.

In an exclusive interview with Rock Center Anchor and Managing Editor Brian Williams, the president recalled the moment when one of the helicopters used by Seal Team Six and special forces encountered problems.

“There’s silence at this point inside the room,” the president told Williams in an interview airing on NBC's Rock Center, “Inside the Situation Room,” on Wednesday, May 2 at 9pm/8 c.  

The raid on bin Laden’s compound in Abbottabad, Pakistan led to the al-Qaeda mastermind’s death.

Secretary of State Hillary Clinton, while glimpsing at the famous photo of her and the president’s top advisors in the Situation Room during the raid, joked that she covered her mouth like “when my husband drags me to an action movie.”

Putting the jokes aside, Clinton said that she stills feels adrenaline rushing through her body when she thinks of the night U.S. forces killed bin Laden.

“What it conjures up is all of the emotions that were running through my and every other person in that small group,” Clinton told Williams.  “It was just an extraordinary experience and a great privilege to be part of.”

Editor's note: Click here to watch the special edition of Rock Center with Brian Williams, 'Inside the Situation Room,' that aired Wednesday, May 2 on NBC.

White House photo by Pete Souza

 Rock Center with Brian Williams has been given unprecedented access to the White House Situation Room and learned new details about the events leading up to the raid targeting Osama bin Laden.

As the one year anniversary of the death of bin Laden approaches, President Barack Obama spoke exclusively to Rock Center Anchor and Managing Editor Brian Williams from the Situation Room, the most secure and secret part of the White House.  The interview, a first for network television, will air during an hour-long Rock Center special, "Inside the Situation Room," on Wednesday, May 2 at 9pm/8c.

White House photo by Pete Souza

The iconic photograph taken inside the Situation Room offered the world the first glimpse of Pres. Obama's national security team at work during the Special Operations mission. Many of the people present in the room on the day bin Laden was killed are speaking to Rock Center about that historic night.

In addition to the president, Brian Williams interviewed Vice President Joseph Biden, Secretary of State Hillary Rodham Clinton, former Chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, National Security Advisor Tom Donilon, Deputy National Security Advisor Denis McDonough and John Brennan, assistant to the president for Homeland Security and Counterterrorism.

Editor’s Note: NBC's Rock Center with Brian Williams, "Inside the Situation Room," will air on Wednesday, May 2 at 9pm/8c on NBC.