Democratic 2020 U.S. presidential candidate and U.S. Senator Kamala Harris (D-CA) speaks during a campaign stop at Keene State College in Keene, New Hampshire, April 23, 2019.

Sen. Kamala Harris ignored pleas from her staff to institute a defendants' rights policy while she served as district attorney of San Francisco, according to a new report in The Wall Street Journal.

According to the report, Harris took no action on memorandums written by her aides in 2005 proposing that her office institute a written policy for disclosing police misconduct to defendants. The disclosures, known as "Brady disclosures" after the 1963 Supreme Court case Brady v. Maryland, were opposed by police unions.

Harris ultimately enacted a Brady disclosure policy years later, but only after a 2010 scandal involving her office's failure to disclose information to defendants led to the dismissal of 1,000 drug-related cases. Superior Court Judge Anne-Christine Massullo criticized Harris at the time for failing to "disclose information that should have been disclosed."

The report sheds new light on Harris' record as a prosecutor and could pose problems for the California lawmaker as she seeks the Democratic nomination for president. Harris has faced scrutiny for her tough-on-crime tactics as attorney general of California and San Francisco district attorney.

Harris responded to that criticism in a speech in South Carolina over the weekend.

"There have been those who have questioned my motivations, my beliefs and what I have done," Harris said. "But my mother used to say, you don't let people tell you who you are. You tell them who you are. So that's what I'm gonna do."

A Harris spokesperson did not respond to a request for comment from CNBC. Her campaign told the Journal, "It took too long to implement, but I am proud we implemented a Brady policy in the D.A.'s office that was later called 'a model for other jurisdictions.'"

Read the full report from The Wall Street Journal.