I'm actually not surprised by at the hung jury. I haven't been following this case a whole lot, but from some of what I've read there are a number of areas in this case that could raise some reasonable doubt.
The unidentified DNA found on the cigarettes at the home, the unidentified hair found on the picture frame, the DNA found on the jewelry box that did not belong to the Young's, the unidentified print on the Tylenol cap, size 10 foot prints, then you have the testimony by the gas station clerk that described a bald man a little taller then herself (which would be approx 5ft ish) and Young was 6ft 1. Then of course you have the time line in which all of this had to be done in and the mileage involved, ect.
This was not a slam dunk case for the prosecution by any stretch of the imagination. imho