Whatever happened to double jeopardy?

How the hell is this legal? A man is put back in prison after decades for the same crime--serving time twice for the same conviction.
Much has changed since then for Richard O'Neal, now 58. After serving four years in prison, he became a popular city maintenance man. His wife was slain. He became a single father, then a grandfather. He built a steady life.
Now O'Neal is back behind bars, though he never committed another crime.
State prosecutors say O'Neal should be punished further in connection with the attack in February 1971. The principle of double jeopardy protects him from being tried again for assault - the crime that sent him to prison in 1972. But prosecutors say they can now prove the shooting was an "overt act" in a broader conspiracy to kill officers.
The arrest of O'Neal, one of nine alleged ex-members of the Black Liberation Army charged in January with conspiracy, has outraged relatives and friends.