Civil rights activists, outraged by a white police detective's acquittal in a black teenager's death, have asked congressional black leaders to look into race relations.

The activists also threatened demonstrations that would fill jail cells with protesters if the police officer, McKenzie Mattingly, successfully appeals his firing by the city's police chief.

"Louisville is a mud hole in the South when it comes to race relations," the Rev. Louis Coleman said Thursday.

The city remained calm after Mattingly was cleared Wednesday night of murder, manslaughter and reckless homicide charges by a Jefferson County Circuit Court jury consisting of 10 whites and two blacks.

Mattingly, 31, shot 19-year-old Michael Newby three times in the back on Jan. 3 when an undercover drug bust went awry. Newby was the seventh black man killed by Louisville police since 1998. Mattingly was the first officer to be criminally charged in any of the shootings.

Mattingly family spokesman Lukas Dwelly said the verdict was welcomed by many who had sympathy for the former officer. Dwelly started a Web site to raise money and support for Mattingly.

"This community has to stick behind its police officers and enforce the law," Dwelly said. "Society has created a need for the police officers of the world to go out and fight the drug problem."

Mayor Jerry E. Abramson urged residents to remain calm.

"You may be disappointed or you may be supportive of the decision, but additional violence will accomplish nothing," he said. "This incident was handled by the book in terms of the criminal justice process."

Activists said they were not surprised by the verdict, but said it demonstrated that the justice system is not colorblind in the city. They accused prosecutors of a halfhearted effort in the case.

The Justice Resource Center, a civil rights group headed by Coleman, prepared a letter for the Congressional Black Caucus requesting hearings delving into race relations in Louisville.

The letter cites the deaths of Newby and James Taylor, a handcuffed black man who was shot 11 times by a city police detective in 2002. Police claimed Taylor lunged at two officers with a box-cutter knife.

The letter states that "racism and classism" are "interwoven in the fabric of everyday life."

"People need to know what type of justice really is going on in this city, and it's been going on for a long time," Coleman said.

Activists scheduled a downtown march Sunday to protest the verdict.

Dwelly expressed sympathy for Newby's mother and said he realized the verdict provoked anger among some. But he said protesters should redirect their efforts "to keep drugs out of people's hands."

Meanwhile, Louisville Police Chief Robert White said he stood by his decision to fire Mattingly in April after the officer was indicted.

Mattingly has appealed his firing to the police merit board, which could overturn the decision. Abramson said the city will defend the police chief's decision "as aggressively as we can."

Mattie Jones, a civil rights activist, said any decision to reinstate Mattingly should spark protests that would "fill up the doggone jail."

"Whatever it costs us, we don't mind that, because we're sick and tired of our children dying in the streets," she said.

McKenzie Mattingly, a former Louisville police detective, was acquitted in the fatal shooting of Michael Newby during an undercover drug buy. Michael Newby, 19, was fatally shot Jan. 3 by Mattingly.