Because of differences in the way corrections systems compile statistics, it is difficult to determine exactly how many people serving life without parole in the United States committed their crimes as juveniles.

• The Rocky Mountain News contacted every state for statistics, and 29, including Colorado, responded. Seven states said they allow life without parole for juveniles convicted as adults but currently have none. An eighth state, New York, allows it but didn’t know if it has any.

• Twenty-one states reported a total of 734 inmates serving life without parole for crimes they committed as juveniles, ranging from one each in five states to 227 in Florida, which has more than 4,700 lifers.

• Colorado, where 46 of its 360 lifers committed their crimes as juveniles, has one of the highest proportions among the states responding.