I can't be sure how this video would be helpful to either the defense or the prosecution but I think both will find ways, IF this thing is legit. Really, I do NOT see how it helps the defense in any logical or sensible way.
For one thing- D. Casey was hired first by Baez, then by the Anthonys. Their paid investigator. Considering the Anthonys repeated, adamant assertions that Caylee was alive and people should "get off their asses" and look for a "live Caylee", one must assume that they were just as adamant that when paying a P.I. they would ask his *advertiser censored* to look for a "live Caylee".
So why was he looking for her in woods and undergrowth at the end of her own street? Why was he following tips about a body, instead of tips about "live Caylee?" Why could or should D.Casey have cared if it "really" was a place where teens hung out?