Highton qualified as a lawyer, procurator and notary in 1966 at the University of Buenos Aires (UBA). Her postgraduate studies were at UBA, Harvard Law School and the University of Nevada. From 1967 she practised as a lawyer and in 1973 she became an official defence lawyer for incapable defendants. In 1979 she became a judge, joining the national Appeals Court in 1994. She taught extensively particularly at UBA, and has written several books largely on civil law.
In June 2004, Highton joined the Supreme Court. She was the first woman to join the Court (under a democratic government), although Carmen Argibay's appointment had been announced earlier. When it came to Senate approval, 51 of the senators present voted for her appointment and five were against. In August 2005 she was appointed vice-president of the Court.
The International Association of Women Judges (IAWJ) awarded her Human Rights Award during a conference held in Seoul on 18 May 2010.
Highton and her husband Alberto Mario Nolasco have two sons.