Its called deduction. There is no Yahoo video with here killing her child. THe correct question is who, other than Casey could have put the tape there?
Are you a lawyer or do you make your living in the justice system?
Last night on Greta she had the prosecutor on. She asked him if he thought the tape was put on Caylees mouth or if it could have moved there over the time. His answer was YES that he agreed that with the body etc being covered with water for a time and animals rummaging around the tape could have moved there from somewhere else. There was no indication that the tape had actually been over her mouth
Now, if even the prosecutor himself is unsure of whether that tape was actually put over her mouth or not and no evidence of who put the tape there in the first place could you assume that maybe the jurors picked up on that? Whether or not you can, if there is doubt even in his mind as to the origin and placement of that tape would you be willing to convict? You see, thats deductive reasoning.