Or if the evidence is coming back as inconclusive or non-existent. This could go either way. I will not draw conclusions one way or the other. I do believe that if the tests came back conclusively they would have charged her and not really needed that new "controversial" Body Farm testing.
I believe that the sample sent to Body Farm for time of death data. The DA in this case would rather file charges when there is a body.
If the time of death could be even estimated, LE could go with phone records, GPS in phone, witnesses, and soil data to determine an area to search. After 31+ days of Casey's moving around, LE needs a smaller area to concentrate on. JMHO