No, I think he is going to claim that the rain rehydraded the body and hatched more flys locally, both making it a likely day for the flys to lay eggs. I don't buy it, but I think that's going to be his line. Well it could be his line, but I'd have to wonder how 0.17" of moisture would do that ?
And since blowflys usually lay eggs within 20 minutes of exposure, you'd have to conclude the body was mummified before it was exposed, then later re-hydrated. Not a good argument for the prosecution.
The thing that limits the earliest date of exposure is the beetle larvae, Faulkner found only the initial generation.
As I said, it doesn't fly with me. The flys would have hit the body before it a chance to dryout, unless it was in a refrigerator, or sealed. Either way somebody has to do something on about the 16th.