Mensa types are said to be good at probability calculation and are certainly aware of the likely penalty for murder in the first degree of a little girl. So, sure, it's possible to do what you describe, but I'd say the risks are a bit large — of being observed as well as of inadvertently leaving physical evidence for the criminalists to find. And, anyway, if DW has such an aptitude for spiriting away little children without leaving behind tracks or witnesses, then why is he up for Murder I in the first place?
Very hard to understand how DW, would abandon humanity to steal a child and kill her, after 50 years of (by most standards) a fairly successful life. He has even designed and patented medical inventions.
In a curious parallel, however, Avila worked at Guidant, a manufacturer of medical devices.
Does this give a glimpse of nisight into their psyches? Do they essentially see other humans as machines, composed of interchangeble parts, existing for thier pleasure?
He also couldn't get rid of the thousands of images of LITTLE GIRLS including LITTLE GIRLS being GANG RAPED BY TEN MEN on his computer, so I'd guess that his sick compulsions were stronger than his intelligence.
So he found himself with a dead girl, and a disposal problem, and even a genius couldn't erase all the evidence.