Here is a look back at unsolved murders that have haunted law enforcement for decades.
Among the homicide cases is the murder of JonBenet Ramsey, the 6-year-old beauty queen found dead at her family's Colorado home. And who sexually assaulted and murdered three young girls during a Girl Scouts trip to Camp Scott in Oklahoma in 1977?
Will police ever catch their killers? Will the families of the victims ever get the closure they need?
Click through to look at the investigations into these heart-wrenching tragedies.