Tamar was a Teaching Fellow with Georgetown University Law Center's International Women's Rights Clinic, where she supervised human rights litigation and fact-finding in a variety of African and Asian countries and authored numerous articles on the rights of women and children. Tamar is a graduate of Stanford University and Harvard Law School, where she was editor-in-chief of the Harvard Human Rights Journal. She has held positions with the American Civil Liberties Union of Southern California, Human Rights First, and the law firm Simpson, Thacher and Bartlett, and served as a law clerk for the Southern District of New York and the Supreme Court of Israel.

She joined Open Society's Law and Health Initiative as a Program Officer in September, 2006. As part of her work, she moderated a program on Health and Human Rights Mechanisms at a conference in South Africa in 2008.