Justice Sybil Hart Kooper was born in Brooklyn around the year 1925, the daughter of Walter R. Hart, a State Supreme Court Justice and Presiding Justice of the Appellate Division, Second Department. She graduated from Wellesley College and New York Law School and practiced with a specialization in family law.
Kooper was appointed to the Family Court in 1973 by Mayor John V. Lindsay. In 1975 she was elected as a Justice of the Supreme Court. She presided over notable murder trials, including the murder of William Turks, a black man, by white youths. Justice Kooper was designated to the Appellate Division, Second Department by Governor Mario M. Cuomo in 1985. She retired in October 1991 due to breast cancer.
Kooper became the first female member of the Metropolitan Trial Lawyers Association after bringing a suit because she had been previously denied admittance on the basis of her sex. She served as President of both the New York State Women Judges' Association and the National Association of Women Judges. In 1986, Kooper was a member of the New York Task Force on Women in the Courts, which investigated gender bias in the courts, including issues such as the courts' response to violence against women, the courts' enforcement of women's economic rights, and the status of women attorneys and women court employees.
At the time of her death she was married to Justice William C. Thompson of the Appellate Division. She had been married twice previously, to Robert Ross and Stanley E. Kooper, and had three sons and a daughter. She died on December 11, 1991 in Brooklyn Heights at the age of 66.
Schafran, Lynn Hecht, and Norma Juliet Wikler. "Operating a Task Force on Gender Bias in the Courts: A Manual for Action." The Foundation for Women Judges, 1986. Web. 10 Feb. 2012. http://womenlaw.stanford.edu/pdf/gender-bias.pdf.
"Summary Report New York Task Force on Women in the Courts." Unified Court System Office of Court Administration, Mar. 1986. Web. 10 Feb. 2012. http://www.nycourts.gov/ip/womeninthecourts/ny-task-force-on-women-in-the-courts-summary.pdf.
"Sybil Kooper, 66, Former Justice in New York Appellate Division." New York Times (1923-Current file): B15. ProQuest Historical Newspapers: The New York Times (1851-2007). Dec 13 1991. Web. 10 Feb. 2012.