True crime shows are not for everyone, but if you are a fan of the genre and a student of critical thinking, this docuseries is for you. It is dark, gritty, loaded with unexpected turns and twists, and is a fascinating historical window into British society in the 1970s. In focusing on one of the most notorious cases in the annals of British crime, The Ripper tries to answer the central question of why the largest and most expensive manhunt in British criminal history failed to catch a brutal and sadistic serial killer known as the Yorkshire Ripper. The Ripper murdered thirteen women and attempted to murder seven others between 1975 and 1981.

The docuseries is a chronicle of bureaucratic obstacles and police missteps that doomed the investigation to failure, and even though the killer, Peter William Sutcliffe, was finally caught, it was purely by accident when he was arrested for an unrelated traffic violation by a local cop who happened to notice a strong resemblance between Sutcliffe and a photofit on the wall of the police station. In the end, thousands of hours of police work involving hundreds of investigators and costing millions of pounds had come up empty. The question is why.

Instead of trying to manipulate viewer emotions through a dramatic reenactment of events or pandering to our morbid fascination with dead bodies by showing grisly crime scenes, The Ripper tries to present the facts and get at the truth through interviews with those involved in the investigation and members of the press and public. There is no narrator to manipulate viewer opinion but only the actual words and opinions of the police, forensic experts, the press and public, and, most important, the surviving victims and the families of the murdered victims. To be sure, no documentary is wholly objective, and that is certainly true of The Ripper. In the last two episodes, a strong feminist point of view does emerge, but it only partially explains the mistakes in critical thinking that doomed the investigation to failure.

The Ripper is a cautionary tale of the pitfalls to avoid not only in criminal investigation but in any inquiry into the truth. There are at least four of them, and they are on full display in the docuseries. The first is the unwillingness or inability of investigators to critically examine their own biases, in this case a strong sexist and classist bias against women of the lower classes. Throughout the docuseries, we see the dominant sexist and classist attitudes of 1970s British culture reflected in the assumptions guiding the investigation and the media covering it.

The second mistake is allowing wishful thinking to contaminate the search for truth. Wanting desperately to catch the killer to stop the carnage and appease an outraged and fearful public driven by lurid press coverage, the police made assumptions and jumped to conclusions based on fear and hope rather than on the evidence. The third mistake is confirmation bias, the powerful tendency of the human mind to consider only evidence that will confirm one’s beliefs and ignore any evidence that will challenge those beliefs. There are many reasons for confirmation bias, but what we see in the Ripper investigation is what is often found in people in positions of power and authority: a self-serving desire to hold on to power coupled with a myopic belief that they know more than their subordinates. This brings us to the final mistake: the dogmatic refusal to admit that one’s assumptions and conclusions could be wrong, one of the cardinal sins in criminal investigation. Instead of treating their assumptions and inferences as tentative hypotheses that can be overthrown in the light of new evidence, the leaders of the investigation consistently refused to consider new evidence brought to their attention that would call their beliefs into question.

What is shocking about the docuseries is how close the police came to apprehending the killer and preventing many of the murders and attacks, only to have the Ripper slip through their fingers. Over the course of the investigation, Sutcliffe was interviewed nine times by police but still failed to make their top forty suspect list. What makes these events so tragic is that if the critical thinking precepts mentioned above had been in place, even just at key moments in the inquiry, most of the deaths and much of the harm inflicted by Sutcliffe would have been prevented.