"The police
have no obligation to order a crowd to disperse before making arrests,
a federal appeals court ruled today, marking a victory for the District
of Columbia in a suit that alleges police unlawfully arrested a group
of demonstrators in January 2005," reports Mike Scarcella in the Blog of the Legal Times.

In a divided opinion, a three-judge panel of the U.S. Court of
Appeals for the D.C. Circuit remanded the suit to the trial court for
further proceedings. The trial judge had granted summary judgment in
favor of the plaintiffs. Click here for the D.C. Circuit opinion.

The appeals court found that there remains material issues of fact
in dispute. The plaintiffs and police tell different stories about how
the plaintiffs ended up getting arrested in an alley the night of
January 20, 2005, in the Columbia Heights neighborhood of Northwest

Some in the crowd took to property destruction.

The plaintiffs,
including Sarah Carr, said they were not involved in any acts of
vandalism. The trial court judge found the arrests of the plaintiffs
violated the Fourth Amendment because the police could not have had
probable cause to arrest certain marchers.

At issue on appeal is the extent to which police need probable cause
to arrest any individual in a crowd when there are people who are
committing crimes. Senior Judge Laurence Silberman, writing for the
majority, said that “police witnesses must only be able to form a
reasonable belief that the entire crowd is acting as a unit and
therefore all members of the crowd violated the law.

Silberman said the police do not first need to order the crowd to
disperse to give non-offenders a chance to comply with the order.

“If police have probable cause to believe that the group they are
arresting is committing or has committed a crime, no more is
necessary,” Silberman wrote. “Requiring a dispersal order in addition
to the ordinary probable cause threshold would be particularly
anomalous in a case like this in which officers have reason to believe
that an entire crowd is engaged in or encouraging a riot.”

"Encouraging" is the key word.  The opinion's summary of the facts shows the police observing that every act of vandalism (dragging newspaper racks into the street, breaking windows, etc.) was greeted by cheers from what appeared to be the whole crowd.