Pershing Park Mass False Arrests
On the morning of September 27, 2002, the D.C. Police Department working with the U.S. Park Police encircled Pershing Park, refused to allow anyone to leave and then arrested and hog-tied peaceful demonstrators, tourists, passers-by, and legal observers. Many were bound wrist to ankle on a police gym floor for upwards of 24 hours.
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Huffington Post: D.C. Police Take A Progressive Approach To Protests. It Wasn't Always That Way.
But the current approach that D.C. police take toward protests did not come about on its own. Instead, the more relaxed attitude is the result of investigations and litigation that came about after the Metropolitan Police Department employed a heavy-handed approach to various protests in the late 1990s and early 2000s.