Attorney General Jeff Sessions stepped into the Bundy prosecution after Wednesday’s mistrial, ordering a third-party examination of the case in light of the latest government snafu.

“The attorney general takes this issue very seriously and has personally directed that an expert in the [Justice Department’s] discovery obligations be deployed to examine the case and advise as to the next steps,” said Ian D. Prior, the department’s principal deputy director of public affairs, in a late Wednesday statement.

The decision to intervene came after Chief U.S. District Court Judge Gloria Navarro declared a mistrial over the government’s “willful failure to disclose information” to the defense, saying it would have been “impossible” for the four co-defendants to receive a fair trial.

“Failure to turn over such evidence violates due process,” Judge Navarro said in the courtroom, the Arizona Republic reported. “A fair trial at this point is impossible.”

Nevada rancher Cliven Bundy, his sons Ammon and Ryan Bundy, and Ryan Payne of Montana have been charged with 15 felony counts stemming from the 2014 armed standoff with the Bureau of Land Management at the Bundy ranch near Bunkerville.

The examination represents the first direct public intervention by the attorney general in the Nevada case, which began last year under then-Attorney General Loretta Lynch.