Many other reviews fault the series for going too far down the conspiracy theory rabbit holes like the ritualistic/Odinism angles the defense team brought up unsuccessfully. But that's the duty of a defense team, especially in such a high profile, high stakes case as this one. That approach obviously caused unnecessary damage to the lives of some innocent people, but the routine, dogged police work ultimately showed that no one else was connected to the crime. The misplaced tip sheet uncovered by the volunteer staffer is another example of how routine police work often plays an important role, rather than the flashy technology and certainty of DNA analysis too often portrayed on TV.
The defense tried to make this discovery seem as if law enforcement had purposely misconstrued an honest attempt to help the investigation by an innocent man into incriminating evidence against an innocent man. But Allen changed his story several times, a classic mistake that incriminated him further at an early stage of the interview process. That gave greater cause to obtain the warrant to search his residence and find the Sig Sauer .40 caliber pistol, ultimately matched to the unspent cartridge found at the scene of the murder. He hadn't known about the cartridge left behind until the later interview when the investigator pointed it out, along with the markings matching it to his weapon. That revelation apparently caused his first admission and realization that "I'm f**ked". Had that information and other data been released to the public at the outset he would have gotten rid of the weapon to eliminate the most important link between him and the crime. The defense rightfully challenged the exactness of such evidence but not sufficiently to dissuade the jury.
The most important link was Libby's phone. At the start of the investigation, law enforcement ONLY released a single image of the "Bridge Guy" a few feet away from them, and the audio of the suspect ordering them "down the hill". But actually Libby had recorded an unbroken sequence from the "Bridge Guy" walking up behind Abby, then Libby suggesting they move off the path and then the "Bridge Guy" ordering them down the hill. They obviously had become wary of this individual but by then it was too late to save themselves. But most importantly the images and audio place NO ONE else at the scene moments before the murders that even remotely resembles any of the alternative suspects offered by the defense or the conspiracy theorists. The combination of all those elements made it difficult for an acquittal even without the confessions Allen made verbally and in writing, regardless of his mental state when he made them. I think the defense put forth a good effort, but the case against Allen was too good. If the defense could have placed someone else at the scene at the time of the murders with forensic or video/photographic/cell phone signal tower data for instance it would have cast reasonable doubt. But they didn't because it likely doesn't exist or else we'd have seen it by now, especially with an army of online sleuths looking at the case from every angle to come up with exactly that sort of evidence.
