Is the US criminal justice system biased?

Protests have spread across the US in the wake of a decision not to prosecute a white policeman for killing an unarmed black teenager. Black leaders say the decision by a grand jury not to indict police officer Darren Wilson over the shooting of Michael Brown in Ferguson, Missouri, shows the justice system is skewed against black people. President Barack Obama has ordered Attorney General Eric Holder to look at what steps could be taken to build trust in communities, and make sure that law enforcement is fair. But critics say Obama has said this in the past, and still has not done nearly enough to help black Americans. We ask how much damage has the case done to race relations in the US? -- Aljazeera