I'm not sure I follow this line of reasoning. AM claimed he was at his mothers home, 20 miles away from the kennels, at the time the murders were committed. But cell phone video shows he was actually on-site and not at his mom's place. The evidence generally points to Paul and Maggie being killed within a few minutes of the video being shot (although the defense may try to argue that point).The lie about not being there at the kennels at 8:44, when he obviously was, does not contradict the alibi.
Sure, now the defense could come up with a brand-new alibi and say that for whatever reason AM lied originally. Maybe the jury will buy their explanation, I don't know. We'll see what happens when the defense team puts on its case.Nothing proves that he was there at the time of the murder, which could have been later than 8:50. An exact time of death has never been established. Yes, it looks bad for him, but it only takes one juror.
But his original alibi, and the only one that's been offered to date as far as I know, was broken by Paul's video.