She received a Bachelor of Arts, with honors, from the University of California, Riverside, in 1991 and a Juris Doctor from Harvard Law School in 1995.

From 2001 to 2014, she served as an Assistant United States attorney for the Central District of California in the Criminal Division.

[3] From 2014 to 2022, she served as a judge of the Los Angeles County Superior Court after being appointed by Governor Jerry Brown.

President Biden nominated Garnett to the seat vacated by Judge Manuel Real, who assumed senior status on November 4, 2018.

[6] On April 27, 2022, the United States Senate invoked cloture on her nomination by a 64–34 vote.