Donald J. Trump has been joined in recent days by entourages of supporters who watch his prosecution in the morning and then give statements backing him outside the courthouse.

On Monday, the daily news conference disintegrated into chaos, when anti-Trump demonstrators and hecklers surrounded the speakers, then effectively silenced them with shouts, whistles and the clanging of a cowbell.

Among the speakers on Monday in Collect Pond Park, across Centre Street from the courthouse’s front doors, were Bernard Kerik, New York’s former police commissioner, who was pardoned by Mr. Trump for eight felonies; Kash Patel, a former Trump administration intelligence official involved in his 2024 campaign; and Rep. Andrew Clyde, a Georgia Republican.

Mr. Clyde said that “the judge is very one-sided,” and Mr. Patel said that the only person harmed had been the defendant: “That victim is Donald J. Trump.”

While many supporters talked in normal voices to the microphones, the effect was largely like a television on mute. The police worked to keep the demonstrators away and physically removed the man with the cowbell after he unfurled a sign that read “Bootlickers.”

Another heckler, referring to six of the seven men wearing Mr. Trump’s trademark blue sport coat and red tie, shouted, “Where do you do your clothes shopping? Dictators ‘R’ Us?”

Despite the police officers’ efforts to allow political speech, all that could be heard were jeers and insults, though the word “sham” could be discerned amid the din.