He was a managing partner of Collier, Halpern & Newberg, LLP, in White Plains, New York,[3] where he focused on commercial, employment, real estate, and securities litigation.

[4] From 2016 to 2017, and again in 2019 and 2022, he was an adjunct professor at the Elisabeth Haub School of Law at Pace University, where he taught "The Anatomy of a Trial: The Burden of Proof.

"[2] Halpern was recommended to the White House by former Westchester County District Attorney Jeanine Pirro, a prominent talk show host who is an outspoken supporter of the Trump Administration and the former wife of Halpern's law firm partner.

President Trump nominated Halpern to the seat vacated by Judge P. Kevin Castel, who assumed senior status on August 5, 2017.

[5] On January 3, 2019, his nomination was returned to the President under Rule XXXI, Paragraph 6 of the United States Senate.