The videos that emerged from an Upper East Side event in October showed a disturbing scene: about a dozen men connected to a far-right group called the Proud Boys surrounding and striking a smaller group of protesters, believed to be self-described anti-fascists.

Ten members and associates of the Proud Boys, which the Southern Poverty Law Center has called a “hate group,” were arrested as a result of the altercation. And this week, two are going to trial in what appears to be the first time members of the group, which have clashed with left-wing opponents in other parts of the country, will appear before a jury to face charges stemming from an attack.

Jurors, however, are unlikely to hear from any of those who were beaten.

The four victims have not cooperated with the authorities, who do not even know their names. They are identified in an indictment only as Shaved Head, Ponytail, Khaki and Spiky Belt.

Phillip Walzak, the Police Department’s main spokesman, said that footage from police body cameras showed that victims refused to talk with officers who sought statements after arriving on 82nd Street as the attacks were taking place.