Blacknell has worked as a Deputy Public Defender in the Los Angeles County Public Defender's Office since 2003 and has handled high-profile cases. She was appointed to represent a man accused of kidnapping Daisy McCrackin. Blacknell's husband, Jovan Blacknell, also works as a criminal defense attorney and has handled several high-profile cases.
Interim public defender appointment
In 2018, the Los Angeles County Board of Supervisors appointed Nicole Tinkham as interim public defender. Blacknell helped organize an effort to put pressure on the Board of Supervisors to remove Tinkham because of her lack of criminal law experience. Following the protests and public criticism, the Board appointed Ricardo Garcia who worked for years in the San Diego County Public Defender's office.
Wiretap Scandal
In July 2018, Blacknell uncovered a secret recording operation inside of an attorney-client interview room. It was later revealed that the operation had been set up by the Los Angeles Police Department in cooperation with a prosecutor from the Los Angeles County District Attorney's Office. In response to the scandal, the Los Angeles County Board of Supervisors voted to send a letter to then sheriff Jim McDonnell to stop the installation of audio-video recording devices inside of lock-up facilities at various criminal courthouses throughout Los Angeles County. The Los Angeles Times responded to the scandal.
Community activism
Bail reform
Blacknell has engaged in activism in the Los Angeles community. She advocated for the release black mothers as a part of the National Black Mama's Bail Out Day campaign. This was a part of the National Bail Out collective, a community-based movement striving to end pretrial detention and mass incarceration. Blacknell believes that the money bail system is unjust and in need of reform. At Community Coalition's People Power Convention, Blacknell said “Ninety-five percent of arrestees plead guilty,” and noted that “studies show that sexual assault and violence happen in the first seven days of an inmate’s incarceration.”
Girls empowerment
Blacknell was the keynote speaker at the “I Matter” Girl Empowerment Conference at East Los Angeles College, aiming to create more female leaders in the community. In her speech, Blacknell discussed her journey to become an attorney. She spoke of being a child of the Crack epidemic surrounded by drugs and gangs and having to overcome feelings of self-doubt.
