The Netflix series “Making a Murderer” impressed director Errol Morris, who knows a thing or two about true-crime documentaries. Morris, whose 1988 film “The Thin Blue Line” helped exonerate a man sentenced to life in prison for a murder he didn’t commit, says “Making a Murderer” succeeds in exposing an egregious example of prosecutorial misconduct. “There’s a large swath of the American public who is unaware of what can actually go wrong in terms of prosecutors bending the rules or not following them at all,” says Morris, who lives in Cambridge. “You make a movie like this, it’s inevitably going to be skewed — and you can’t argue it isn’t — but it presents something really, really powerful that needed to be presented. The way this case was handled was shameful. Whether [ Steven Avery ] is guilty or innocent, it’s disgraceful.” Morris said he doesn’t know enough about the case to have an opinion about Avery’s guilt or innocence, and he thinks that’s a shortcoming of the series. “That you could go to 10-plus hours and have so little material that has a bearing on that issue is hard to understand, but to me the series is about something different.” What it’s about, he says, are the same issues he dealt with in “A Wilderness of Error,” Morris’s door-stop-thick book about the dubious prosecution of physician Jeffrey MacDonald, who was convicted of killing his wife and children and has been in prison since 1982. “There are so many resemblances,” he said. “An extraordinary amount of prosecutorial misconduct.” Morris is currently working on a six-part Netflix series himself. What’s it about? “True crime,” he said.