Was looking back over a series of WAVY articles that included interview commentary from Wells worth looking over.
It does seem that the polygraph reliance was not the only serious mistake leading to a cold case. mistakes, LE turf wars and heel-dragging on evidence sharing played a role. 30 Years Later: The Colonial Parkway Murders — Part 2
They mention that investigators thought the killer had died or gone to prison since there were no more murders after 1989.
New methods today that solve cold cases reveal that many spree and serial killers sometimes are still alive and free decades after their crimes. We now know that some killers take a long hiatus, especially if they fear getting caught. Joseph D'Angelo (GSK), Rex Heuermann, etc. JMO, it's why more cold cases need to be investigated with modern tools. Doing so provides experts with much more information about the behavior of killers, how they evade detection, why they stop.