Devin Almonor, the teenage son of a former police officer, said he was thrown against an unmarked car and temporarily handcuffed walking home from a bus stop. Medical student David Floyd was frisked by officers outside of his apartment as he helped a neighbor locked out of his home.

For both, the experience was humiliating and frightening — and they say — illegal because they believe they were stopped because of their race. Both are Black.

"I am not a criminal. I did not commit any criminal acts," said Floyd, who testified along with Almonor at the opening of a federal trial Monday challenging the constitutionality of some encounters under the controversial law enforcement tactic of stopping, questioning and frisking New Yorkers on the street.

Police have made about 5 million stops during the past decade, mostly of Black and Hispanic men. Lawyer Darius Charney of the Center for Constitutional Rights which filed the suit in 2008 on behalf of Floyd and three others, called many of the stops a "frightening and degrading experience" that violates the civil rights of many New Yorkers. The class-action lawsuit seeks broad reforms to the practice, and asks for a court-appointed monitor to oversee the changes.