Krishnadev Calamur

Updated at 10:46 a.m. ET

The U.S. Supreme Court, in a 5-4 opinion, says the sedative used in Oklahoma's lethal injection cocktail does not violate the U.S. Constitution's ban on cruel and unusual punishment.

Here's the background to the case, in the words of SCOTUSblog:

Updated at 10 a.m. ET

The shootout involving motorcycle gangs last weekend in Waco, Texas, resulted in 170 arrests and put a spotlight on the gangs' history, which dates back to the 1940s.

Former Arkansas Gov. Mike Huckabee announced Tuesday that he is seeking the Republican presidential nomination.

"It seems perfectly fitting that it would be here that I announce that I am a candidate for president of the United States of America," he told a crowd of supporters in his hometown of Hope, Ark., which is also Bill Clinton's hometown.

Huckabee, who previously ran for the presidency in 2008, hosted a television program on Fox News until January, when he ended the eponymous show to consider his political future.

Updated at 5:20 p.m. ET

President Obama offered his "grief and condolences" to the families of the American and Italian aid workers killed in a U.S. counterterrorism operation in January. Both men were held hostage by al-Qaida.

"I take full responsibility for a U.S. government counterterrorism operation that killed two innocent hostages held by al-Qaida," Obama said.

Former Secretary of State Hillary Clinton announced today that she is seeking the Democratic presidential nomination for the 2016 election.

The National Rifle Association, which supports Second Amendment rights, is holding its annual convention in Nashville, Tenn., this weekend. So it came as a surprise to see headlines that said the expected 80,000 people attending the gun-rights group's convention will not be allowed to carry their firearms.

The truth, as it turns out, is more complicated.

Updated at 12:30 p.m. ET

Sen. Rand Paul, R-Ky., announced today that he will seek the 2016 GOP presidential nomination.

"I have a message — a message that is loud and clear and does not mince words," he told supporters in Louisville, Ky. "We've come to take our country back."

Updated at 12:34 p.m.

Sen. Harry Reid, D-Nev., the Democratic leader in the Senate, said he won't seek re-election next year.

Updated at 3:15 p.m. ET

The co-pilot of Germanwings Flight 4U 9525 appears to have deliberately crashed the plane carrying 150 people into the French Alps after the pilot had left the cockpit, Marseille prosecutor Brice Robin said at a news conference Thursday.

Texas is ending its contract with the Daughters of the Republic of Texas to run the Alamo. The San Antonio Express-News is reporting that the move ends the organization's more than 100-year-long management of the landmark.

The change will help "create a bigger, brighter future for this Texas shrine," Texas Land Commissioner George P. Bush said in a joint statement with the DRT.

The Ferguson, Mo., City Council removed John Shaw as city manager today following last week's U.S. Justice Department report that accused the local police and justice system of racial bias.

Jason Rosenbaum, a reporter for St. Louis Public Radio, tweeted the news of the City Council resolution that removed Shaw from his position.

Updated at 1:16 p.m.

Actor Leonard Nimoy, best known for his role as Mr. Spock, the logical half-Vulcan, half-human in the original Star Trek series and several movies, has died at his home in Los Angeles, his granddaughter, Madeleine, told NPR. Nimoy was 83.

The cause was end-stage chronic obstructive pulmonary disease, she said.

NPR's Neda Ulaby, who is reporting on the story, tells our Newscast unit:

A New York jury took a little more than three hours today to convict Ross Ulbricht, the San Francisco man linked to the shadowy online marketplace Silk Road, of seven drug and conspiracy counts.

Prosecutors said the website, which had been labeled the eBay of the drug trade, allowed drug dealers and others to anonymously reach a broader base of customers. The Associated Press adds:

Updated at 5:04 p.m. ET

The U.S. Supreme Court will decide on gay marriage this term.

The justices said today they will review an appellate court's decision to uphold the ban on same-sex marriage in Ohio, Tennessee, Michigan and Kentucky. The four states are among 14 that ban same-sex marriage.

Updated at 2:39 p.m. ET

President Obama announced today the most significant change in U.S. policy toward Cuba in more than 50 years, paving the way for the normalization of relations and the opening of a U.S. Embassy in Havana.

Obama said "we will end an outdated approach that for decades has failed to advance our interests and instead we will begin to normalize relations between our two countries."

Residents of Denton, Texas, voted Tuesday to ban hydraulic fracturing in the city.

According to unofficial results posted on the city's website, 58.64 percent of voters supported banning the controversial drilling method that is also called fracking; 41.36 percent voted against the proposition. It's the first time a city in the energy-friendly state has voted to ban fracking.

The vote is expected to be challenged, but Mayor Chris Watts said he would defend the ban.