Scheck was born in Queens, New York, and grew up in Port Washington, New York. He graduated from the Horace Mann School in Riverdale, New York in 1967. He went on to receive a B.A. from Yale University in 1971 (majoring in Economics and American Studies) and a Master of City Planning (M.C.P.) and Juris Doctor (J.D.) from University of California, Berkeley in 1974.

Scheck was the personal Lawyer for the Hedda Nussbaum case, in 1987. He both defended her and assisted in getting the charges against her dropped, while also assisting in ensuring Joel Steinberg's arrest and suing him in the civil case, Nussbaum vs. Steinberg. Scheck was part of the team that defended O. J. Simpson in his 1995 trial. He was associated with the clearing in 1999 of Dennis Fritz and Ron Williamson who had spent 11 years in prison of wrongful murder convictions. He was lead Lawyer who defended British au pair Louise Woodward in her 1997 murder trial.

Scheck co-founded the Innocence Project in 1992 with Peter Neufeld, also his co-counsel on the O.J. Simpson defense team. The Project is dedicated to the utilization of DNA evidence as a means to exculpate individuals of crimes for which they were wrongfully convicted. To date, 343 wrongful convictions have been overturned by DNA testing thanks to the Project and other legal organizations. The Innocence Project does not use legal technicalities to challenge convictions; the Project accepts only cases in which newly discovered scientific evidence can potentially prove that a convicted person is factually innocent.

Scheck is a professor at the Benjamin N. Cardozo School of Law, where he established the first Innocence Project. He is Director of Clinical Education for the Trial Advocacy Program and the Center for the Study of Law and Ethics, and a former staff attorney at the Legal Aid Society of New York. From 2004–2005 he served as President of the National Association of Criminal Defense Lawyers. In 1996 he received the Robert C. Heeney Award, the "NACDL's most prestigious award... given annually to the one Criminal defense attorney who best exemplifies the goals and values of the Association, and the legal profession" They get thousands of letters from wrongly convicted inmates every year.

More recently, he served as attorney of the wrongly accused Duke University lacrosse player Reade Seligmann to represent him in a civil lawsuit filed on October 5, 2007 against the city of Durham, North Carolina, and its former district attorney, Mike Nifong. He also was responsible for clearing John Restivo, Dennis Halstead, and John Kogut after 18 years in prison for the 1985 Lynbrook rape and murder of Theresa Fusco, when DNA evidence proved them innocent and implicated others.