The Manhattan U.S. Attorney’s Office has confirmed in a court filing that it would request a special master be appointed to review sensitive material recovered from former New York City Mayor Rudy Giuliani’s home and office during an early morning raid in late April.

The move, which would allow a neutral referee to make determinations about what potential evidence can be reviewed by investigators, comes amid what observers expected to be a sticky legal battle over what attorney-client privilege matters may attach to Giuliani, the one-time U.S. attorney for the Southern District of New York turned personal lawyer to former President Donald Trump.