Migration of larvae IS a whole area of concern in forensic entomology. Were there recently dead animals near the body when it was found? Even then, I don't think they are likely to migrate before completing their life cycle in their original food source. At any rate, the entomologists involved knew exactly what species they were dealing with, and the dissenting entomologist never brought up any possible migration of larvae that I know of. Or did he?
...their original food source in the garbage container was very limited...just like desert conditions would naturally be.
I saw one adult fly carrying them and the rest were on the floor going in various directions!
I've seen the mealy bugs-fly do the same thing...just crawling though---big time!