On May 29, 1971, two 17-year-old girls hopped into an old Studebaker, headed to a party at a gravel pit outside of Vermillion, S.D., and disappeared. The community was shocked by how the girls had seemingly vanished down a country road.

In the early 2000s, a cold case unit decided to reinvestigate, thinking they might find new evidence, which KARE 11's Lou Raguse covered as a young reporter for a Sioux Falls television station. Prosecutors aggressively pursued a suspect already imprisoned for multiple rapes, charged him with murder, and suggested that family members had helped with the coverup.

In 2013, a curious civilian's discovery helped finally determine what happened to the girls. That compelled Raguse to write his first book, "Vanished in Vermillion," to set the record straight, restore the reputation of the unjustly accused — and make amends for his role in that process.

Raguse's book traces the case's many bizarre twists and turns, involving everything from false memories conjured through hypnosis to a perjured jailhouse informant. Raguse shows how law enforcement's and prosecutors' blunders and biases impeded their ability to solve the mystery. And he explores the all-too-human attitudes that led to various mistakes. This interview has been edited for length and clarity.

Q: What made you think this case would make a good book?
A: Back when I covered the cold case investigation, I was hearing all these rumors about crazy false memories and I didn't know what to believe. It really wasn't until after it was discovered what happened to the girls that I felt like there was so much that was left unsaid. And also people did not take responsibility for mistakes that happened.

Q: Why did you focus on the investigation, vs. simply explaining how it was resolved?
A: I wanted to help give a window into the human condition of why people do what they do or defend what they defend. For example, there was one major detective who, even in the face of all the evidence at the end, refused to change his position. That was disturbing to me. But I think it also reflects how a lot of other officers who make a mistake and refuse to acknowledge the mistake might feel.

Q: Why did law enforcement initially put very little effort into finding the girls, then later try to track down even the most tenuous leads?
A: With the initial investigation, they just thought the girls ran away. But later on, they were convinced that the girls were murdered. So in both cases, they were basically looking for evidence that confirmed what their theory was, and they didn't quite have it proven. So every lead that came along that looked like it might help prove what their theory was, they went all in, whether that meant flying to Texas or Canada to try to interview people, or investigating a blurry picture.

Q: How did you see confirmation bias play out as the cold case unit investigated?
A: The suspect had been convicted of doing horrible things. And that is one thing I hope readers will think about: What kind of justice does somebody deserve when they have done horrible things but may be innocent of another thing that they're accused of? If you believe in the American criminal justice system, you have to believe that they deserve justice, too. But human nature might not be to treat them the same.

Q: How did law enforcement's shaping of the narrative mislead the public?
A: It was beyond implying stuff. For much of the case, I thought that I was reporting on a potential serial killer based on what they were telling us. In the end, I felt lied to. In hindsight, it really makes you remember to question a lot more what the narrative is instead of believing it. But if the reporters are getting fooled, then the public is getting fooled, that's just the nature of our job.

Q: Why weren't you initially more skeptical of the authorities' narrative?
A: The families of the girls were wanting the case to be solved. And when you are reporting and you're working with them, you want to see them get the answers that they're looking for. And it feels like they're so close, so even questioning the narrative is uncomfortable when you're in the moment. It's a lot easier to do after the fact. Also, I think that because of my age and inexperience, I didn't really know how to cover a story or a case when I figured out that there was not good police work. That was a big reason for me wanting to do the book, to personally fix what I felt was my inadequate reporting.

Q: In the process of writing the book, you reflected on your own biases and apologized to the suspect's brother. What impact did that have?
A: It's funny how our human nature is to want to justify what we did, and how we did it, because at the time I thought I was doing the best job I could. The suspect's brother hated my guts and being able to see how his demeanor changed after I took responsibility and apologized showed me how important that element is to other people. Self-reflection is important. And this book shows how so many people just haven't done that.