My initial reaction to the creation of a "likely killers" list is a good one. I would like to know where the list is. Part of the deal with a validity of such list is for police to have a group to target. The public needs to know who these people are and react. Either it will allow them to know who to avoid or it will hopefully make some people who are interacting with criminals to stop and help catch them when they break the law.
I am slightly conflict on the civil liberties concern, but I've not yet seen this as a problem, as long as the list is based on criteria determined from public information.