Martha and Alvaro Galvis used to travel from New Hampshire to Boston to watch the marathon every year. Both were hurt in the bombing two years ago. Jesse Costa/WBUR hide caption

itoggle caption Jesse Costa/WBUR

A memorial at the site of the first explosion in the Boston Marathon bombing. Defense attorneys say too many people in the potential jury pool have some kind of personal connection to the case. Andrew Burton /Getty Images hide caption

itoggle caption Andrew Burton /Getty Images

Boylston Street's 26-mile marker will be a welcome sight to the thousands of runners who are in today's Boston Marathon. Today marks the 118th running of the race. Jared Wickerham/Getty Images hide caption

itoggle caption Jared Wickerham/Getty Images

Blue and yellow are the colors for tributes to victims of the Boston Marathon. Street lights on the route of this year's race are among the places they're showing up. Andrew Burton/Getty Images hide caption

itoggle caption Andrew Burton/Getty Images

Carol Downing is still haunted by memories of last year's marathon. But she's excited about reuniting with other survivors. Michael Dwyer/AP hide caption

itoggle caption Michael Dwyer/AP

Boston bombings suspect Dzhokhar Tsarnaev on April 19 as he emerged from a boat stored in a Watertown, Mass., backyard. The red dot of a police sharpshooter's laser sight can be seen on his forehead. Mass. State Police Sgt. Sean Murphy/Boston Magazine hide caption

itoggle caption Mass. State Police Sgt. Sean Murphy/Boston Magazine

Boston bombings suspect Dzhokhar Tsarnaev on April 19 as he emerged from a boat stored in a Watertown, Mass., backyard. The red dot of a police sharpshooter's laser sight can be seen on his forehead. Mass. State Police Sgt. Sean Murphy/Boston Magazine hide caption

itoggle caption Mass. State Police Sgt. Sean Murphy/Boston Magazine

Boston bombings suspect Dzhokhar Tsarnaev emerges from a boat stored in a Watertown, Mass., backyard on April 19. The red dot of a police sharpshooter's laser sight can be seen on his forehead. This is among the images that Massachusetts State Police Sgt. Sean Murphy gave to Boston Magazine. Mass. State Police Sgt. Sean Murphy/Boston Magazine hide caption

itoggle caption Mass. State Police Sgt. Sean Murphy/Boston Magazine

Boston bombings suspect Dzhokhar Tsarnaev on April 19 as he emerged from a boat stored in a Watertown, Mass., backyard. The red dot of a police sharpshooter's laser sight can be seen on his forehead. Mass. State Police Sgt. Sean Murphy/Boston Magazine hide caption

itoggle caption Mass. State Police Sgt. Sean Murphy/Boston Magazine

April 20 in Watertown, Mass.: Investigators work in and around the boat in which Boston bombings suspect Dzhokhar Tsarnaev was found hiding. Darren McCollester/Getty Images hide caption

itoggle caption Darren McCollester/Getty Images

Some of the graves at the Al-Barzakh Islamic Cemetery in Doswell, Va., where the body of Boston Marathon bombings suspect Tamerlan Tsarnaev has been buried. His grave was not identified to journalists. Yuri Gripas /Reuters /Landov hide caption

itoggle caption Yuri Gripas /Reuters /Landov

FBI Special Agent in Charge Richard DesLauriers (at the microphones), Boston Police Commissioner Edward Davis (standing, at far left) and other authorities briefing the news media on April 19. That's the day Boston bombings suspect Tamerlan Tsarnaev was killed and his brother, Dzhokhar, was captured. Neal Hamberg /Reuters /Landov hide caption

itoggle caption Neal Hamberg /Reuters /Landov

Tamerlan Tsarnaev, as seen in a video taken on April 15 near the finish line of the Boston Marathon. FBI.gov hide caption

itoggle caption FBI.gov

Boston Police Commissioner Edward Davis. Michael Reynolds /EPA /LANDOV hide caption

itoggle caption Michael Reynolds /EPA /LANDOV

This image from a surveillance video, taken near the finish line of the Boston Marathon, helped investigators identify Tamerlan Tsarnaev (in black cap) and his brother, Dzhokhar (in white cap), as the main suspects in the bombings. FBI.gov hide caption

itoggle caption FBI.gov