An agent filed an application Thursday seeking access to a laptop belonging to Akeem Cruz, of Brooklyn.
Cruz is one of the last people to have been with 22-year-old Megan Waterman, of Maine, the weekend she disappeared after traveling to a hotel in Hauppauge to meet clients for sex.
Months later, she and three other prostitutes were found dead, their remains scattered along a beach road.
In the court filing, agents didn't mention the killings, but said they were seeking evidence of sex trafficking.
Cruz is currently jailed in Maine on an unrelated drug charge.