One thing to keep in mind in Colorado is that the laws regarding a minor having a driver's license is that anyone between the ages of 16-21 has to hold a driver's permit for 12 months and during that 12 months, the driver can ONLY drive with an adult. So, if AS's date of birth is January 17, 1995, the soonest he could have gotten a driver's permit would have been January 17, 2011 (and he'd have to have the permit a full 12 months). The soonest he could have gotten an actual driver's license would have been January 17, 2012.
It certainly doesn't mean that AS wasn't driving around prior to January 2012, I just think it may not have been very likely that any crimes that occurred prior to him having a driver's license and were further away (like the lady who went missing in July 2011 up on Highway 6 in the foothills) are probably not as likely as crimes he could have done on foot (possibly the 2010 Kentner Lake attempted abduction).
http://www.colorado.gov/cs/Satellite/Revenue-MV/RMV/1209548240333