In We Keep the Dead Close: A Murder at Harvard and a Half Century of Silence (Grand Central, Nov.), Cooper delves into the 1969 murder of Harvard student Jane Britton, which was finally solved in 2018.

How did the appeal of a certain theory and your wanting to believe it influence your investigation?

Part of my job, as I saw it, was to track down as many people in Jane’s life as possible and to understand what they believed happened to her, and why they believed it. As they were telling their stories, I let myself be swayed by the seductiveness of their narratives. If I understood their theory enough to be momentarily persuaded by it, then I could take the time to test whether or not it actually worked. In the light of this scrutiny, the desired narrative often fell apart, and then I had two areas to investigate: why were these stories so believable and seductive if they weren’t true, and what truly happened to Jane?

Are you proud that your doggedness in seeking access to the records of the case led to getting the DNA test performed that confirmed the murderer’s identity?

I am very happy my records push was partially the reason that the tests were done, and that they produced a result, and now those who knew and loved Jane can have a name. I’m especially thankful that it happened in Jane’s brother’s lifetime. In order to prove to us that the case was active and ongoing, to oppose the records request, the Middlesex DA needed to conduct an examination of whatever evidence they had that stood a chance of yielding a culprit. In this case it was a minute amount of DNA. They exhausted the crime scene DNA in this last round of testing. Thankfully, it was enough.

Would you describe your interest in the murder as obsessive at times?

I can see how my interest in the murder would have to be deemed obsessive. I was absolutely committed to knowing everything I could about Jane and her case. But––and maybe obsession is always like this––it didn’t feel that way from the inside. I imagine obsession as this dark preoccupation, one that keeps me up at night and gnaws at my dreams. It was never really like that with Jane. It felt more like a responsibility. At first the murder seemed like a terrible open secret that just needed one person to pay attention. Then, by the time I figured out exactly how difficult her case was going to be to solve, I’d already become very enamored with Jane, and the sense of responsibility shifted to her and to those who loved her. I had to take it as far as it would go.