[3][4] Moriarty worked briefly as a reporter before enrolling at Macalester College, where she played softball and basketball and majored in history and political science, earning her Bachelor of Arts in 1986.

Moriarty's office forced Hennepin County Attorney Mike Freeman and the Minneapolis Police Department to stop the stings, which many viewed as racially biased.

[12] In 2020, Moriarty's office conducted a study that revealed Black people were overwhelmingly more likely to be stopped by police for traffic violations—even though White drivers were more likely to have contraband.

[13] On December 23, 2019, Minnesota State Public Defender Bill Ward announced that he was placing Moriarty on indefinite suspension.

[14] The Minnesota Board of Public Defense hired a law firm to investigate allegations that she had posted offensive content on social media, created a fearful environment in her office and fractured relationships with criminal justice leaders.

[21] On September 1, 2021, Hennepin County Attorney Mike Freeman announced that he would retire at the end of his term after 24 years in the role.

[25] A nonpartisan primary was held on August 9, 2022, with Moriarty and former judge Martha Holton Dimick advancing to the general election.

[24] On November 14, 2022, Moriarty announced that State Representative Cedrick Frazier and law professor Mark Osler would serve as co-chairs of her transition committee.

[27][28] In a notable case from March 2023, Moriarty offered controversial plea deals to a 15 and 17-year-old charged with second-degree murder after shooting Zaria McKeever in Brooklyn Park.

The plea deals allowed the defendants to serve 18 to 24 months in a juvenile correctional facility, with probation upon release until the age of 21.

[29] Moriarty's decision was criticized by the family of the murder victim, Attorney General Keith Ellison, Minnesota's largest police association, and community activists, who felt betrayed by what they viewed as lack of accountability for the killers and a miscarriage of justice for survivors.

[39][40] Moriarty acknowledged that only the attorney general could issue a binding opinion, but pointed out that a judge may rule differently in court.

Moriarty had retained Jeffrey Noble as her expert, who had previously testified for Ramsey County prosecutors that the shooting of Philando Castile was unreasonable.