U.S. Supreme Court Chief Justice John Roberts will not testify at an upcoming Senate Judiciary Committee hearing expected to focus on judicial ethics, he said in a letter on Tuesday to the committee chair.
The committee's Democratic chairman, Dick Durbin, had asked the chief justice to appear before the panel to address potential reforms to ethics rules governing the justices. The senator cited "a steady stream of revelations regarding justices falling short of the ethical standards."
Roberts said he would "respectfully decline" the invitation, adding that such appearances by chief justices were exceedingly rare given concerns about the separation of powers between the three branches of the U.S. government.
A Supreme Court spokesperson issued the response, which included five pages of information about current judicial ethics standards.
Durbin had earlier asked Roberts to investigate ties between Justice Clarence Thomas and a wealthy Republican donor.
Thomas, the longest serving of the court's nine justices, has been under pressure after published reports by news outlet ProPublica detailed his relationship with Dallas businessman Harlan Crow, including real estate purchases and luxury travel paid for by Crow.
The recent reporting has raised questions over potential conflicts of interest for the justices and the court, which has endured escalating criticism because it lacks a formal ethics code.
"Supreme Court ethics reform must happen whether the Court participates in the process or not," Durbin said in a statement responding to Roberts' letter. "It is time for Congress to accept its responsibility to establish an enforceable code of ethics for the Supreme Court, the only agency of our government without it."