In a nationwide poll of police by the National Institute of Justice, 61 percent said officers “do not always report even serious violations by fellow officers,” and 67 percent said whistle-blowers were likely to be “given a cold shoulder.”

So why should bad guys and ordinary citizens pay heed when police and prosecutors lecture them about how it’s their civic duty to come forward with information about crimes? If law enforcement officers won’t think of themselves as righteous whistle-blowers rather than as rats or snitches, how can a system that depends on witness testimony possibly function?

“My sense as a prosecutor is that whenever you deal with any organization, there’s a high likelihood of running into that kind of resistance,” says Prince George’s State’s Attorney Glenn Ivey, whose job it is to put together the case against whoever killed Findley’s accused murderer, Ronnie White. Faced with officers who won’t talk, Ivey says he uses the same tools he deploys against street thugs: “You find the little fish and try to flip them; you try to get the less culpable to testify against the more culpable in exchange for lighter punishment.”

Prosecutors say there’s an important distinction between why cops and citizens in high-crime areas don’t talk.

On the street, “people don’t talk because they really don’t trust the police,” says Alan Strasser, a Washington trial lawyer who was formerly chief of the felony division of the U.S. attorney’s office in the District. “They sometimes see them as an occupying army. Or they’re afraid of physical retaliation or at least some social retaliation, being ostracized, if they talk.”

Law enforcement officers, in contrast, “feel they are fighting a battle against crime and they don’t have the resources or support they need to do their job, and because of that, they face unique tensions,” Strasser says. “As a result, a few of them feel they’re entitled to a little slack, to do things that other people can’t do.”