How much power do prosecutors have?

Emily Bazelon is a New York Times Magazine staff writer and author of "Charged: The New Movement to Transform American Prosecution and End Mass Incarceration," a new book that examines prosecutorial power, and how that has affected the justice system for decades.

Bazelon told Boston Public Radio Tuesday that prosecutors have contributed to mass incarceration in America, due in part to an increase in sentences stemming from the 1980s that shifted discretion to the hands of prosecutors.

“The problem is you can’t eliminate discretion from the system. It moved to prosecutors, because once you know what the mandatory sentence is, then it depends on the charge and the plea bargain. And charging and plea bargain are fully in the hands of prosecutors, so we really shifted this balance of power,” Bazelon said.

A survey from the American Civil Liberties Union found that more than 80 percent of voters think Massachusetts needs to reform its criminal justice system, but only about 40 percent of voters know that district attorneys are elected and accountable only to voters.

“We should think of the DA like the mayor: someone who is answerable to us, who has a tremendous influence over how our community feels, what it’s like, how people experience the criminal justice system,” said Bazelon. “Just that piece of knowledge is really powerful.”

Bazelon said that progressive district attorneys, like Suffolk County District Attorney Rachael Rollins, could be part of the solution to mass incarceration.

Rollins was elected on a campaign of discretionary prosecution, choosing to decline charges for a number of smaller offenses and instead prioritize resources to violent crimes.

Read more: 'Jail As A Last Resort': Rachael Rollins Defends Plan Not To Prosecute Certain Crimes

Rollins has been in the news lately for pushback from public safety officials for her platform, and is currently challenging U.S. Immigration and Customs Enforcement’s authority to detain undocumented people in courtrooms.

“She’s answering to a different constituency. It was really communities of color, people impacted directly by the system, who came out and elected her. She’s accountable to them, and to the rest of the county, too,” said Bazelon. “But, I think if people feel like her approach is successful, if it feels like the community is still safe and healthier in a kind of sociological way, that is going to help her get reelected, and then you see more longer path change.”