In 1993, Sax received her undergraduate degree from the University of California, Santa Barbara, and her juris doctor in 1997 from Pepperdine University School of Law.

She was admitted to the State Bar of California on November 24, 1997. The same year, she joined the Riverside County District Attorney's Office. In 1999, she left to work for the Los Angeles District Attorney's Office, where, for more than 10 years, she prosecuted sexual offenders. She left the district attorney’s office in 2009.

Since 2005, she has been an instructor for the Los Angeles Police Department, Los Angeles County Sheriff’s Department, and the California District Attorneys Association. She is also a lecturer at the University of California, Los Angeles’ paralegal program and an adjunct professor of criminal justice at California State University, Los Angeles.

In addition, she sits on a multi-disciplinary team at UCLA's Rape Treatment with Department of Children and Family Services, law enforcement, victim advocates, and social workers. In March 2010, she was a speaker at the Conference on Crimes Against Women in Dallas, Texas. She was a trainer at the California Sexual Assault Investigators Association 2010 Spring Conference.

She currently is an NBC News legal analyst as well as a regular legal commentator on Nancy Grace, Larry King Live and FOX News. Sax also has a weekly radio show, “Justice Interrupted.” She represents the parents of teenager Amber Dubois, who was murdered in San Diego County in 2009 by convicted killer John Albert Gardner, and appeared on Larry King Live with Dubois' mother, Carrie McGonigle. She currently represents Samantha Spiegel in an alleged stalking case against John Mark Karr, who falsely confessed to killing Jon Benet Ramsey. She's also regularly asked to debate high-profile criminal cases, including for "Good Morning America" and ABC News.

She was featured on ABC public radio's "The Law Business Insider," hosted by Steve Murphy in 2008 to discuss the Caylee Anthony case.

Sax has authored six books, including It Happens Every Day: Inside the World of a Sex Crimes DA and The Complete Idiot's Guide to the Criminal Justice System.

She is a regular contributor to the Huffington Post. She has also contributed legal commentary on CBS News' Crimesider. And she's a regular contributor to Women in Crime Ink, which the Wall Street Journal called "a blog worth reading."

She lives with her husband and three children in Los Angeles.