Shenker was a Russian Jewish immigrant who arrived in St. Louis in 1922 with limited English. He was educated at Washington University in St. Louis, and set up law practice in 1932. Shenker built a reputation as a successful defense attorney, raised money for the Democratic Party and for Israel, and co-founded the Dismas House charity in St. Louis.
Shenker first came to national attention during the Kefauver Hearings in the early 1950s, in which he represented a number of underworld figures. From 1962 Shenker represented Jimmy Hoffa, and in 1966 became Hoffa's chief counsel.
In 1970 a year-long Life Magazine investigative report accused him, as head of the St. Louis Commission on Crime and Law Enforcement, along with the city's mayor Alfonso J. Cervantes, of both having "personal ties to the underworld." The magazine alleged that Shenker controlled the massive $700 million Teamsters Union Pension Fund and its investments, most notably in Las Vegas but also in San Diego (through developer Louis Lesser), New York, Kansas City, and elsewhere. Shenker himself assumed part ownership of the Dunes Hotel and Casino for a few years.
On a local level, Shenker and Mayor Cervantes were part-owners of the mid-town St. Louis landmark Continental Life Building, along with businessman Harold Koplar, owner of independent television station KPLR-TV and Shenker's brother-in-law. Shenker's wife, Lillian Koplar Shenker, had also attended law school at Washington University, and became a judge in her own right in the St. Louis Court of Criminal Corrections.
Shenker died of pneumonia, at his daughter's house in Santa Monica, California, after a long illness. Fictionalized versions of Shenker appear in the 1961 film Hoodlum Priest (as "Louis Rosen", founder of a fictionalized Dismas House), and in the film Casino.
- New York Times obituary, August 11, 1989
- Life Magazine, May 29, 1970, pages 24-31