Democratic presidential candidate Kamala Harris has said her experience as a prosecutor has given her insight into trying to improve the criminal justice system and distinguishes her in a crowded field vying to take on Donald Trump.

“We’ve got to hold this guy accountable by prosecuting the case in front of the American people against four more years of this administration,” Harris told the South Carolina conference of the National Association for the Advancement of Colored People (NAACP) on Saturday night.

“And I’ve prosecuted a lot of cases. But rarely one with this much evidence.”

Among 23 contenders for the Democratic presidential nomination, the California senator placed fifth in a CNN-Des Moines Register Iowa poll released on Saturday night. Attracting 7% support, she trailed South Bend, Indiana, mayor Pete Buttigieg (14%), Massachusetts senator Elizabeth Warren (15%), Vermont senator Bernie Sanders (16%) and former vice-president Joe Biden (24%).

Iowa holds the first vote in the Democratic primary. South Carolina, another early voting state, has a Democratic electorate that is primarily African American. In her speech, Harris appealed to anyone skeptical of her background as a district attorney and state attorney general who was notably tough on crime.

Harris has been criticized for being too tough on the accused when she was San Francisco district attorney and California attorney general. In her campaign rollout earlier this year, she sought to answer such criticism by saying “too many black and brown Americans are locked up” and suggesting she supports major change.

Echoing that sentiment on Saturday, she said her motivations have been questioned.

“But my mother used to say, ‘Don’t let people tell you who you are,”’ she said. “‘You tell them who you are.’ So that’s what I’m gonna do.”

Noting that her love for the law came from an attorney uncle, Harris said that like him she “wanted to be the person who people called for help, to solve their problems, to protect people, and to fix what is wrong”.

Harris noted that some within her own family questioned her decision to become a prosecutor, saying she “had to defend that decision like one would a thesis”.

She said she knew prosecutors had not always treated black people the same as white people and “looked the other way in the face of police brutality”. But she said her presence and perspective had helped white colleagues see issues more fully.

“So I knew I had to be in those rooms,” she said. “We have to be in those rooms even when there aren’t many like us there.”

Harris also addressed black voters directly, saying she hears their concerns about safety and criminal justice.

“Everyone wants the police to respond when their home gets burglarized,” she said. “Everyone wants accountability when a woman is raped, when a child is molested, and when one human being kills another.

“What we do want is a justice system where no one is above the law, not even the president of the United States.”