[3] Foxx ran for the State's Attorney's office on a platform of criminal justice reform, and has often been termed a "reformist", "reform-minded", or "progressive" prosecutor alongside others such as Larry Krasner, Rachael Rollins, Chesa Boudin, Aramis Ayala, Kimberly Gardner, Diana Becton, and Satana Deberry.

[11][16] In 2013, she was hired as deputy chief of staff for Cook County Board President Toni Preckwinkle, focusing on criminal justice issues.

Foxx campaigned on a platform of criminal justice reform, emphasizing policies such as diverting low-level offenders to treatment programs rather than prisons, address wrongful convictions, and dealing more aggressively with police misconduct.

[42] That same month, Foxx's office announced that prosecutors would no longer request pretrial detention for those charged with low-level nonviolent offenses in court.

[45] Since then, case-level data on felony intake, initiation, disposition, and sentencing, along with summary reports and dashboards, have been posted on the State's Attorney office's website.

[46][47] A series of reports by The People's Lobby and Reclaim Chicago, progressive organizations who had endorsed Foxx in 2016, found that the number of sentences involving prison time in Cook County dropped 2.5% from 2016 to 2017 and 19% from 2017 to 2018.

[41] Early in her first term, Foxx established a program called the Gun Crimes Strategies Unit (GCSU), which placed specially trained prosecutors directly in police districts.

[53][54] In 2019, analysis by the University of Chicago Crime Lab found that charges for habitual gun offenders increased in the five districts with the GCSU program.

[57] In January 2019, Foxx announced her support for the proposed legalization of recreational marijuana use in Illinois, and helped to write the provisions of the law pertaining to past convictions.

[63] The proposed expansion was partly in response to developments that would enable the State's Attorney's office to address conviction challenges based on allegations of torture by former Chicago police commander Jon Burge.

The policy adopted a "presumption of dismissal" for certain low-level charges (e.g. disorderly conduct, public demonstration, unlawful gathering, curfew violation) and a "presumption against proceeding unless body-worn camera footage is available and/or where a police officer is the complainant" for more serious charges (e.g. resisting or obstructing arrest, assault, battery, aggravated battery, mob action, obstructing identification) that arose during protests.

[65][66] Foxx's challenger in the 2020 election, Republican candidate Pat O'Brien, criticized this policy and argued that it allowed "crime and looting to intermix with peaceful protests.

Smollett orchestrated a staged assault and filed a false report with the local police; Foxx's recusal, due to her "familiarity with potential witnesses in the case", prompted criticism from her predecessor Anita Alvarez.

[76] In April 2023, after two car thieves, age 14 and 17, drove recklessly and killed Cristian Uvidia, a 6-month-old child who was in another vehicle, ABC News Chicago said, "The two have been charged with just one misdemeanor count of criminal trespassing each.