Police Corruption

I do not think the police have an obligation to participate in internal investigations about corruption. The people involved in the corruption are probably themselves or someone they know so they would be more likely to "forget something" or leave out important information that could skew the investigation. Police officers are too close to the crime and where it is happening to be involved. 

I do think police officers should be more open about issues involving corruption to outsiders, but not insiders. The consequences would be that some of their fellow officers could be caught, but if they want to do the right thing, then that won't matter. If officers want to stop the problem, they should tell people outside the department because they will be more likely to actually find a solution and stop the problem. If they tell people inside the department, the chances of them doing something about it and acting on it is slim.