Originally Published: 09 MAR 23 10:49 ET

By Casey Gannon, Sara Murray and Katelyn Polantz, CNN

(CNN) -- Attorneys for former President Donald Trump are at the federal courthouse in Washington on Thursday for a sealed proceeding on whether his defense attorney must answer more questions from a grand jury, according to a source familiar with the proceeding.

The hearing, before Chief Judge Beryl Howell, relates to whether Trump's defense attorney Evan Corcoran must further testify on his interactions with the former president in a grand jury investigation into the handling of classified documents.

The proceeding is one of several closed-door attempts by the Justice Department to get more answers from people close to Trump in criminal investigations. Trump has largely lost these proceedings before Howell opposite Jack Smith's special counsel investigation.

Trump attorneys John Rowley, Jim Trusty and Corcoran are all at the courthouse.

Rowley told CNN on Thursday he was scheduled for a hearing before Howell, but declined to provide any other information because the proceeding was under seal.

Prosecutors have asked the court to force Corcoran to answer questions he declined to respond to in a recent grand jury appearance as a witness. Corcoran declined to answer some questions that would have divulged his advice to Trump and their conversations, citing attorney-client privilege, CNN has reported.

To overcome Corcoran's resistance, the prosecutors have argued to the federal court that Trump may have used his attorney in furtherance of a crime or fraud, a weighty accusation in the ongoing investigation.

Their pursuit comes as part of the special counsel investigation into the handling of classified documents at Mar-a-Lago after the Trump presidency, and possible obstruction of justice.

Corcoran first testified to the grand jury in January and was asked about what happened in the lead-up to the August search of Trump's Mar-a-Lago residence.

Corcoran had drafted a statement in June that attested Trump's team had done a "diligent search" and there were no more classified documents at Trump's Florida residence.

After that, the FBI searched Mar-a-Lago and found hundreds of government records, including classified material, raising questions about the lawyer's attestation.