WASHINGTON — The Supreme Court ruled unanimously today that witnesses who lie to a grand jury are protected from civil lawsuits, giving them the same protection that witnesses get at trials.

The justices ruled against Charles Rehberg, an accountant who was indicted three times involving charges that he harassed doctors affiliated with a south Georgia hospital system.

After the third indictment was dismissed even before a trial, Rehberg sued local prosecutors and their investigator, James Paulk. Rehberg said that he was placed under investigation because of the hospital’s political connections and that Paulk’s false grand jury testimony led to the indictments.

But Justice Samuel Alito said Rehberg’s lawsuit should not go forward. Witnesses are protected from civil lawsuits over what they say in trial testimony. “Grand jury witnesses should enjoy the same immunity as witnesses at trial,” Alito said. “This means that a grand jury witness has absolute immunity.”

Prosecutors also generally are immune from civil lawsuits for anything that relates to a trial.

Lying under oath can subject someone to criminal charges. That was not at issue before the high court.