First and foremost, no evidence in record that any other children can testify to being in there (I would expect the defense to trumpet this if there were). No evidence that any adults witnessed children entering.
The lack of finger prints by Danielle if she did play in there, there should be more. Especially in that so many un I'd prints were found.
The presence of the hair in the trap. The likelihood that a hair would have shed, plus found its way in the drain, plus got caught and not washed down is slim to none in my opinion.
THe presence of the blood or blood like substance.
The combined presence of three unlikely sources of physical evidence that are each unlikely to be left strains my ability to see this as reasonable.
Hair in trap = 80% a single hair was dropped (at rate of 1 every 15 mins), 50% chance it landed in place other than carpet (where it would be vaccumed), another 50% chance Westerfield wash floor, picked up hair and rinsed it in sink, 25% chance the single hair lodged in trap. .80*.50*.50*.25=.05%,
The chance of leaving behind two blood or blood like spots while playing in van ? 20% each or 4% for two.
The combined chance that all three occured on one visit (.80*.05*.04)= 0.16% chance.