[2] After law school, McNulty served as a law clerk for Judge Frederick Bernard Lacey of the United States District Court for the District of New Jersey.

In 1998, McNulty returned to private legal practice, serving as a partner in the Newark, New Jersey law firm Gibbons P.C.

[2][3] On December 16, 2011, President Barack Obama nominated McNulty to a federal judgeship on the United States District Court for the District of New Jersey to fill the seat vacated by Judge Garrett Brown Jr., who assumed senior status on January 2, 2012.

[4] McNulty is the brother in-law of New York senator Chuck Schumer.

Senator Frank Lautenberg submitted McNulty's name for consideration late in the process, and some anonymous commentators suggested that it was a political move to ensure Lautenberg had the future support of Schumer.