In her 2015 autobiography, “The Senator Next Door: A Memoir from the Heartland,” Ms. Klobuchar wrote that she would usually decide who to charge and what sentences to seek in her office’s biggest and “trickiest” cases. But her campaign did not respond to questions this week about what role she played in the Burrell case. It did not come up in Tuesday night’s debate in South Carolina.

On Monday, Mike Freeman, who succeeded Ms. Klobuchar as Hennepin County attorney and won a conviction at Mr. Burrell’s second trial, defended the case as a “solid police investigation and prosecution.” He said that he believed it was “inappropriate and unfair” that the case had become an issue in Ms. Klobuchar’s campaign.

Some of her rivals for the Democratic nomination have also come under sharp criticism for their records on criminal justice, including Michael Bloomberg, who apologized earlier this month for supporting the widely derided stop-and-frisk policy while he was mayor of New York.

Civil rights leaders in Minneapolis say the Burrell case was just one example of how Ms. Klobuchar’s office focused disproportionately on prosecuting African-Americans while declining to bring charges in more than two dozen shootings and other civilian fatalities that occurred during encounters with police officers.

“There is an entire community that suffered under her leadership, and she has refused to accept accountability for the harm that she caused,” said Nekima Levy Armstrong, a civil rights lawyer and former president of the Minneapolis N.A.A.C.P.

In a statement, Ms. Klobuchar’s campaign said that as a prosecutor she had also focused on reducing gun violence, including backing measures opposed by the N.R.A.; prosecuting white-collar crimes, including tax evasion and the financial exploitation of older people; and working with the Innocence Project to improve interrogations and eyewitness identifications.

Her agenda while in office was similar to many other tough-on-crime prosecutors of the era who also embraced the “broken windows” theory of policing. That theory, now widely criticized for packing jails with people of color, held that cracking down on vandalism and other visible signs of minor crimes would lead to a reduction in more serious offenses.