Stith is married to Judge Jose Cabranes of the United States Court of Appeals for the Second Circuit , and is the sister of Laura Denvir Stith, who serves on the Missouri Supreme Court .

Stith received an a Bachelors degree from Dartmouth College in 1973, a law degree from Harvard Law School in 1977 and a Masters of Public Policy from the Kennedy School of Government also in 1977. She clerked for Judge Carl McGowan of the U.S. Court of Appeals for the District of Columbia and for Supreme Court Justice Byron R. White.

Stith began teaching at Yale Law School in 1985.

Her interest in criminal procedure has led her to serve as an adviser to the American Law Institute's Model Penal Code Sentencing and, following an appointment by the Chief Justice of the Supreme Court of the United States, on the Advisory Committee for the Federal Rules of Criminal Procedure. She has also participated in the National Research Council's Committee on Law and Justice, the state of Connecticut's Professional Ethics Committee; the Permanent Commission on the Status of Women in Connecticut; the Women's Campaign School at Yale; and the Connecticut Bar Foundation (as President). Stith served on the Dartmouth College Board of Directors and as Deputy Dean of Yale Law School.

She was one of the witnesses who testified in favor of Sonia Sotomayor during her Supreme Court confirmation hearings.

Stith has published extensively in law journals. Her book, Fear of Judging, written with her husband Jose Cabranes, won a Certificate of Merit from the American Bar Association in 1999.