Trump lawyer ordered to testify in classified documents case in landmark ruling, sources say

A federal judge has ruled that a lawyer for former President Donald Trump must provide additional testimony before a federal grand jury investigating Trump's handling of classified documents, sources familiar with the matter told ABC News.

Special counsel Jack Smith's prosecutors asked Judge Beryl Howell last month to pierce attorney-client privilege and compel Trump attorney Evan Corcoran to appear before a grand jury, sources previously told ABC News.

NOTE: The video in the media player is from a previous report.

The Justice Department made the request on the basis of the crime-fraud exception, sources said, which allows for claims of attorney-client privilege to be pierced in cases where it is suspected that a lawyer's legal services were rendered in the commission of a crime.

Howell said in Friday's order that the DOJ has met the threshold of the crime-fraud exception, according to sources familiar with the matter.

A spokesperson for Trump slammed the decision.

"Whenever prosecutors target the attorneys, that's usually a good indication their underlying case is very weak. If they had a real case, they wouldn't need to play corrupt games with the Constitution," the spokesperson said. "Every American has the right to consult with counsel and have candid discussions -- this promotes adherence to the law. We will fight the Department of Justice on this front and all others that jeopardize fundamental American rights and values."

Trump's attorneys and Justice Department investigators appeared for oral arguments on this matter before Judge Howell last week, sources said. The proceedings were under seal and not open to the public.

Howell's decision effectively affirmed that there's enough evidence that Corcoran's legal services on behalf of Trump were potentially used in the commission of a crime to overrule Corcoran's assertions of attorney-client privilege -- a development that could bolster any future effort by the special counsel to seek criminal charges as part of his investigation, sources said.

Trump's attorneys are expected to ask the D.C. Circuit Court to stay the ruling, pending appeal, sources said.