The Justice Department’s Executive Office for Immigration Review’s case backlog more than doubled over the last 10 years to more than 500,000, and while part of that increase was due to a rise in caseloads and legal complexity, shortages of resources, especially employees, also contributed, GAO has said.

While the office has made certain management improvements including better use of technology, it “does not have effective practices for hiring new immigration judges, which has contributed to immigration judges being staffed below authorized levels.”

While the office currently has 374 authorized immigration judge positions, 86 of those were vacant as of fiscal 2016, it said.

The average time to hire is above two years, GAO said, involving a complex process that includes a review of candidates by a panel of Justice Department officials and a second review after further vetting by another Justice office and by the FBI. Newly hired judges complete fewer cases as they are learning on the job, it added.

Meanwhile, it said, 39 percent of immigration judges already are eligible to retire.