Denver police are under growing scrutiny after a string of fatal shootings, the latest being a developmentally disabled teen and a man officers say was wielding a pickax. Family members say it was a twig. City Council President Elbra Wedgeworth and other council members are calling for a federal investigation. Denver District Attorney Bill Ritter says Colorado law makes it difficult to convict officers.

Ritter has cleared officers in all of the more than 90 shootings over the past decade. Ritter says officers can use deadly force if they have a reasonable belief that their lives are in danger. Jeff Dorschner, a spokesman for the U-S Attorney, says in general the Justice Department waits until local investigations are complete before reviewing cases.

The U-S Attorney is already reviewing the case of Paul Childs, the developmentally disabled teen who was fatally shot by Denver police July 5th as he held a knife outside his home.