I was also disappointed that the documentary took a bias towards Avery being innocent. I wish they'd left it more undecided, more murky, and more honest. Even if there was compelling video evidence, it would still be a fascinating story of incompetence and misconduct throughout the investigation.
Even if you believe Avery to be guilty (as I lean towards), you can't help but to sit in awe as officials motivated to lock up their case almost cost themselves a verdict based on their own actions. It's a story with no heroes.