Saris was a law clerk for Judge Robert Braucher of the Massachusetts Supreme Judicial Court from 1976 to 1977.

She was in private practice with the law firm of Foley, Hoag & Eliot in Boston from 1977 to 1979, served as Staff counsel to the United States Senate Committee on the Judiciary from 1979 to 1981, and then returned to private practice with the firm of Berman, Dittmar & Engel, P.C.

[4] In 2008, Saris sat by designation with the United States Court of Appeals for the First Circuit in the case of Cook v. Gates,[6] which upheld the "Don't ask, Don't tell" (DADT) policy (Title 10, Section 654) against due process and equal protection Fifth Amendment challenges and a free speech challenge under the First Amendment, and which found that no earlier Supreme Court decision held that sexual orientation is a suspect or quasi-suspect classification.

[7] Saris concurred with the majority regarding due process and equal protection, while dissenting with the rejection of the First Amendment challenge, because "if the Act were applied to punish statements about one's status as a homosexual, it would constitute a content-based speech restriction subject to strict scrutiny" and that "the availability of an administrative remedy does not defeat a First Amendment claim that the government is systematically applying the Act in such a way that it unconstitutionally burdens protected speech".

[8] In April 2010, President Obama nominated Saris as Commissioner and Chair of the United States Sentencing Commission.