Lawrence Weiss was born on July 29, 1932 in the Bronx, New York, the son of Orthodox Jews from Hungary who had emigrated in the early 20th century.
Judge Weiss grew up in Elizabeth, New Jersey during the Great Depression. He attended Thomas Jefferson High School, where he played on the basketball team that won three Union County Championships. Judge Weiss graduated from high school in 1949.
He attended Rutgers College as a commuter and played freshman basketball under Coach Bob Sterling. Judge Weiss made the varsity basketball team, coached by Don White, in his sophomore year but then struggled with injuries as an upperclassman. He lived in the Phi Sigma Delta fraternity house. In 1954, he graduated from Rutgers College with a degree in education.
Judge Weiss served in the U.S. Air Force as a navigator onboard the RC-121 Constellation, which was involved in early warning systems. He was in the service until 1957.
Following his military service, Judge Weiss attended law school at Rutgers-Newark, earning his law degree in 1960.
Early in his law career, Judge Weiss worked as a litigator, first for the law office of John Taylor and then in private practice in Westfield. Judge Weiss served two terms as a Democratic councilman in Westfield. In 1973, Judge Weiss worked on the successful gubernatorial campaign of Brendan Byrne.
In 1976, he was sworn in as a Union County District Court judge, and then in 1980, he was appointed to the Superior Court.