As a teenager in the mid-1990s, Damien Echols dabbled in Wicca and wrote love spells in his journal. When three 8-year-old boys — Stevie Branch, Michael Moore and Christopher Byers — were found dead in the woods in West Memphis, Ark., police immediately focused their investigation on Mr. Echols and his friends Jason Baldwin and Jessie Misskelley, Jr. They were pentagram-doodling, Metallica-listening nonconformists in their Bible Belt community, and they were charged despite the lack of any physical evidence tying them to the crime scene and a dozen witnesses placing them elsewhere.

During the murder trial, prosecutors painted Mr. Echols as the ringleader of a satanic group that had murdered the boys in an occult ritual. Mr. Echols, who seems congenitally unable to be anyone other than himself, didn’t do himself any favors on the stand. When the prosecutor asked if he read books by Aleister Crowley, “a noted author in the field of satanic worship,” Mr. Echols said no, then added, “I would have read them if I saw them.” In 1994, he was found guilty of the boys’ murders and sent to Death Row. Mr. Baldwin and Mr. Misskelley both received life sentences.

Thanks to three HBO documentaries about the case, the convicted men became known as the West Memphis Three, and their cause found supporters throughout the country, including a number of high-profile celebrities such as Johnny Depp and Eddie Vedder.

Mr. Echols had dropped out of school in the ninth grade, but he used prison as a kind of monastic retreat and an opportunity for self-directed study. He read about the Hermetic Order of the Golden Dawn, the 19th-century occult group that counted Crowley, W.B. Yeats, Bram Stoker and Arthur Conan Doyle as members. He began practicing the Golden Dawn’s highly choreographed rituals, tracing pentagrams in the air while invoking the names of angels. The Wicca of his youth soon seemed goofy and uninformed.