Robert Galvan, who is on death row for murder, speaks to members of the media at the Adjustment Center yard during a media tour of California's Death Row at San Quentin State Prison in San Quentin, California December 29, 2015. America's most populous state, which has not carried out an execution in a decade, begins 2016 at a pivotal juncture, as legal developments hasten the march toward resuming executions, while opponents seek to end the death penalty at the ballot box. (Photo by Stephen Lam/Reuters)

A woman wearing leggings with the colours of the US flag walks along a street of Havana on February 18, 2015. President Barack Obama announced Thursday he will make a landmark visit to Cuba on March 21-22, pledging to address human rights as America pursues a historic thaw with its former Cold War foe. (Photo by Yamil Lage/AFP Photo)

People look at a man, who residents said was killed by al Qaeda militants, hanging on a bridge in Yemen's southeastern city of Mukalla June 17, 2015. Al Qaeda militants in Yemen killed two alleged Saudi spies, residents said, accusing them of planting tracking devices which enabled the assassination of the group's leader in a suspected U.S. drone strike. (Photo by Reuters/Stringer)

This file photo provided on Sunday February 15, 2015 by the Syrian anti-government activist group Aleppo Media Center (AMC), which has been authenticated based on its contents and other AP reporting, shows Syrian rebels firing locally made shells against the Syrian government forces, in Aleppo, Syria. (Photo by AP Photo/Aleppo Media Center)

“Mountain Goats, Colorado”. A herd of mountain goats huddle together on top of Mount Evans, Colorado during a lightning storm. This photo was selected out of more than 5,000 entries to go on display in “Wilderness Forever: 50 Years of Protecting America’s Wild Places”, a new photo exhibition at the Smithsonian’s National Museum of Natural History, which will run through summer 2015. (Photo by Verdon Tomajko/Smithsonian Wilderness Forever Photo Contest)

Matthias Broda, inventor and designer of the wooden e-bike, cycles a prototype along a street in Berlin, November 20, 2014. The wooden e-bike produced by German company Aceteam from ash wood, will be launched on the market by spring 2015 and will cost around 3,950 euro (4,950 dollars). The e-bike will be equipped with an 250W e-bike motor for a range of up to 100 kilometer (62 miles) with a rechargeable battery. (Photo by Fabrizio Bensch/Reuters)

A devotee takes a holy bath in River Saali in Sankhu on the first day of Swasthani Brata Katha festival in Kathmandu January 5, 2015. During the month long festival, devotees recite one chapter of a Hindu tale daily from the 31-chapter sacred Swasthani Brata Katha book that is dedicated to God Madhavnarayan and Goddess Swasthani, alongside various other gods and goddess and the miraculous feats performed by them. (Photo by Navesh Chitrakar/Reuters)

Pontoons, which were previously used as a floating jetty, are seen on the cracked ground of the Atibainha dam, part of the Cantareira reservoir, during a drought in Nazare Paulista, Sao Paulo state February 12, 2015. Brazil's worst drought in 80 years has left the Cantareira system, that provides greater Sao Paulo with most of its water, with the lowest water level on record. Brazil's economy is already expected to post zero growth this year. Worse yet, since Brazil depends on hydroelectric dams for about three quarters of its electricity, power shortages are also possible due to the drought, federal officials have said. (Photo by Paulo Whitaker/Reuters)