Professor Rhonda Copelon, who has died aged 65 of ovarian cancer, was a path-finding human rights lawyer and activist, and one of the world’s foremost legal scholars of the rights of women. Her ideas have entered the mainstream of human rights law and practice, including at Amnesty International, where I was privileged to benefit from her advice and encouragement.

Despite the important cases she brought before the courts, the most influential aspect of her work may prove to be her academic writing of the mid-1990s. Rhonda argued that states should be accountable under human rights law as much for the crimes by private citizens that they passively allow to happen – particularly acts of violence against women, such as domestic violence, or attacks by armed groups – as for the crimes they actively commit through police, army or other state officials. Already these concepts of state responsibility are being incorporated into the work of UN human rights institutions and advocacy groups.

Born in New Haven, Connecticut, Rhonda was the only child of Herman and Katherine Copelon. She graduated from Bryn Mawr women’s college, Pennsylvania, in 1966 with a degree in history and political science and received her law degree from Yale University four years later.

Rhonda’s early legal career was spent at the Center for Constitutional Rights (CCR) in New York. In the late 1970s, with her colleague Peter Weiss, she brought a groundbreaking civil action for damages, Filártiga v Peña-Irala. Seventeen-year-old Joelito Filártiga had been tortured to death by police in Paraguay. While both Norberto Peña-Irala, the police chief involved in the killing, and Joelito’s sister Dolly were living in the US, Rhonda brought proceedings against Peña-Irala, using an old, rarely invoked provision that gave US courts jurisdiction over any suit brought by a foreign national for wrongful actions “committed in violation of the law of nations or a treaty of the United States”.

The US court of appeals awarded damages of more than $10m, stating that “the torturer has become – like the pirate and slave trader before him – hostis humani generis, an enemy of all mankind” and opening US courts to human rights claims. Even though this was a compensation case, rather than a criminal prosecution, it was an important precedent for cases such as that against General Augusto Pinochet, the former president of Chile, in the 1990s.

Remarkably, the Filártiga decision was handed down on the same day, 30 June 1980, as one of the hardest losses of Rhonda’s career, the US supreme court judgment in Harris v McRae. This was a class action on behalf of women living in poverty who needed publicly funded (Medicaid) abortions. Rhonda’s argument was that it was impermissible to prefer the potential life of a foetus to the health and life of a pregnant woman. The supreme court prohibited Medicaid reimbursement for almost all abortions, even where a pregnant woman’s health is gravely endangered or she is pregnant as a result of rape or incest.

After the blow of the decision in McRae, Rhonda became increasingly committed to exploring the possibilities of international human rights law to secure justice for women. In 1983, she was a founding member of the Central University of New York’s law department, and in 1992 she co-founded the department’s International Women’s Human Rights Clinic (IWHRC). Under her leadership, the clinic enabled students and activists around the world to participate in a range of precedent-setting human rights legal and advocacy campaigns to stop gender and sexualised violence, and to advance reproductive and sexual rights, along with wider economic and social rights.

Outrage at the rape of women in former Yugoslavia and Rwanda in the early 1990s was a spur to action. In the international courts dealing with those situations, the IWHRC argued that rape can constitute torture and genocide. IWHRC teams brought acute awareness of the realities of women’s experience to bear in the three key UN meetings of the 1990s – on human rights (Vienna, 1993), population and development (Cairo, 1994), and women’s rights (Beijing, 1995).

Notably, in 1996, Rhonda brought proceedings on behalf of nine individuals and the Rassemblement Algérien des Femmes Démocrates (RAFD) against the Islamic Salvation Front (FIS) of Algeria and its leader, charging the FIS with war crimes and crimes against humanity, including murder, rape and torture. Though the defendants managed to have the case struck out, this outstanding case recognised and sought a remedy for the grave harms to women caused by religious fundamentalists. Until the end of her life, Rhonda worked on behalf of women subjected to violence by fundamentalists and consistently challenged human rights organisations such as Amnesty International to document and campaign on violence against women by fundamentalist groups.

In 1997, she cofounded the Women’s Caucus for Gender Justice, an organisation that brought the experiences of women in armed conflict to the negotiations establishing the international criminal court. This work ensured that women’s experiences were taken into account in the court’s definition of crimes, rules of procedure and evidence, and that steps would be taken to ensure that women were represented in equal numbers to men as judges and court personnel.

Rhonda had a gentle, sweet-toned voice, but a legal and political analysis as fresh and bracing as spring water, relentless in looking at a problem in all its practicalities. She gave loyal and generous attention and friendship to many clients, students and colleague activists around the world, but especially in South America and Algeria. While she leaves no immediate family, she is survived by a close network of friends who cared for her during her final illness.

Lisa Gormley

• Rhonda Copelon, lawyer, teacher and activist, born 15 September 1944; died 6 May 2010