William Roughead wasn’t the kind of writer who liked to indulge in outrage. The Glasgow lawyer, who began attending murder trials in 1889 at the age of 19—for curiosity’s sake until it became his professional avocation—much preferred to write about crime in a dry, droll manner. The cases he covered, with notable defendants such as Madeleine Smith, Constance Kent, and Katherine Nairn, were colorful enough to speak for themselves, the evidence substantive enough for readers to reach their own conclusions. Over six decades writing about the most notable criminal proceedings in Britain (the best of these essays are collected in Classic Crimes), Roughead did not need to juice his style with the seeds of anger. That’s why so many, myself included, regard him as the dean of the modern true crime genre.

CONAN DOYLE FOR THE DEFENSE: THE TRUE STORY OF A SENSATIONAL BRITISH MURDER, A QUEST FOR JUSTICE, AND THE WORLD’S MOST FAMOUS DETECTIVE WRITER by Margalit Fox Random House, 352 pp., $27.00

But the Oscar Slater case was different. Roughead not only attended the trial of Oscar Slater in Glasgow in May 1909, writing it up for the Notable Scottish Trials series, but he also believed that the guilty verdict, arrived at after barely an hour of deliberation, was wrong. There was, in Roughead’s estimation, no evidence that Slater, a German Jewish immigrant, was even in Glasgow when Marion Gilchrist, a wealthy woman in her 80s, was robbed and bludgeoned to death in her apartment. And the main witnesses, notably Gilchrist’s maid Helen Lambie and a neighbor, Mary Barrowman, kept changing their stories. Even when Slater’s original death sentence was commuted to life imprisonment, Roughead’s outrage did not subside.

Roughead broadcast his disbelief in Slater’s guilt from the first, to anyone who would listen, enjoining the most famous detective fiction writer in the world, Sir Arthur Conan Doyle, in his cause. The case transformed Roughead from observer to participant. He even testified at a hearing, nearly 20 years after the original trial, to determine Slater’s ultimate fate: Would the man stay in Peterhead Prison for a crime he did not commit, or would he finally be freed? Years after that verdict came in, Roughead wrote a fresh essay—his fourth—on the affair in 1935. He was not shy about casting blame for the cascade of injustices that bedeviled Slater, nor did he hesitate to give credit where it was due. For Conan Doyle’s advocacy of Slater, Roughead called him a “paladin of lost causes and champion of forlorn hopes.”

Slater’s plight foreshadows so many future wrongful conviction stories, in which belief that the system will ultimately work is shattered by its cruel unfairness, its sacrifice of innocent defendants at the altar of wins and losses. The case never quite fell out of cultural consciousness—certainly not in Britain, and Scotland in particular, where the sustained outcry led to criminal justice reforms, including the institution of a proper appeals court. This year, his story has been having something of a revival, with a BBC radio documentary by crime writer Denise Mina and Margalit Fox’s splendid new book Conan Doyle For the Defense. How, both ask, despite the flimsiest of circumstantial evidence, was Slater so obviously and badly railroaded? And how did the very people who set out to defend Slater end up turning against him?

Conan Doyle For the Defense cannot resist structuring itself as a detective novel, though the whodunit is less about who killed Marion Gilchrist and more about who framed Oscar Slater. The ingredients are too good to pass up: a famous detective novelist actually playing detective, a man serving time for a murder he did not commit, and a criminal justice system slowly, and reluctantly, reckoning with the advent of forensic science—fingerprints were around when Slater was arrested and convicted, but in one of so many missed opportunities to right the wrong, never used.