A majority of people in the U.S. believe murderers should be put to death, but support for the death penalty is lower than it has been in nearly two generations, according to a nationwide survey released Thursday by the Pew Research Center. The poll found that 56 percent of Americans favor the death penalty for people convicted of murder, a decrease of six percentage points since Pew’s last survey, in 2011. Thirty-eight percent of Americans oppose the death penalty, according to the latest survey.

Throughout the 1980s and 1990s, support for the death penalty frequently topped 70 percent, according to Pew. In 1996, 78 percent favored it, while 18 percent were opposed. The shift in opinion comes as jurors in Massachusetts are set to begin next week the penalty phase of convicted Boston Marathon bomber Dzhokhar Tsarnaev. Tsarnaev, 21, was found guilty on all 30 federal criminal charges, including using weapons of mass destruction, in the 2013 attack that killed three people and wounded at least 170. Nearly half of 1,084 respondents in a nationwide public opinion poll conducted after Tsarnaev’s April 8 conviction said he should die. 

Pew’s survey, conducted among 1,500 adults from March 25 to 29, found that much of the decrease in death penalty support has been among Democrats. Currently, 40 percent of Democrats favor the death penalty, while 56 percent oppose it. In 1996, Democrats favored capital punishment by a wide margin, 71-25. Republican support for the death penalty also decreased, Pew said, although the decline wasn't as steep. Seventy-seven percent of GOP voters favor the death penalty, compared with 87 percent who favored it in 1996.

Other key findings in Pew's latest survey include a concern among 71 percent of Americans that the death penalty risks an innocent person being put to death. About half of Americans say that minorities are more likely than whites to be sentenced to death for similar crimes, while 41 percent think that whites and minorities are equally likely to face death for heinous crimes.