House Oversight Chair James Comer has subpoenaed former President Joe Biden’s White House physician to appear for a deposition later this month, according to a copy of the subpoena letter shared with CNN.

House Oversight and Government Reform Committee Chair James Comer (R-Ky.) issued a subpoena on Thursday for testimony from former President Biden’s White House doctor, Kevin O’Connor. It’s Comer’s latest move to expand his panel’s probes into Biden’s mental acuity.