True crime runs on explanation. Every case gets a why, and where one is missing a plausible substitute is usually supplied: a childhood, a grievance, a pathology. Nine entries in this archive record that no motive was ever established, and they are worth reading as a group because the honest answer is uncommon enough to be interesting.
Two things are notable straight away. Six of the nine are women, in a roster where women are a small minority. And these are not unsolved cases, where the motive is missing along with everything else. In four the killer was convicted and the question still has no answer. In a fifth she was arrested, tried and found not criminally responsible. In the remaining four nobody was ever prosecuted, because the killer died the same day or was among the dead.
Vickie Dawn Jackson is the clearest of the convictions. She was a nurse in Nocona, Texas, and ten or more patients died of injections of a muscle relaxant. She pleaded no contest and was sentenced to life in 2006. No motive was ever established. The entry notes that several of the ten were people who had slighted her or her family, and one was her estranged husband's grandfather, which is the shape of a motive without being one, since it accounts for some of the deaths and not the rest.
Maoupa Maake is the case that resists categorization most completely. Convicted of twenty-seven murders in South Africa out of thirty-five charged, he is described in his own entry as atypical because he had no fixed victim type and no fixed weapon, and no motive was ever established. Serial murder is usually classified by pattern. His entry is a record of a man who did not have one.
Marcel Barbeault killed eight people in Nogent-sur-Oise between 1969 and 1976. No motive was ever established and no sexual assault was involved, which removes the explanation that would ordinarily be reached for.
Caroline Grills poisoned members of her own family in Sydney with thallium. No motive was ever established: no insurance, no inheritance, no dispute anyone could identify. She was convicted, sentenced to death, commuted, and died in prison in 1960 without the question being answered.
Sanna Sillanpaa shot three men at a Helsinki shooting range in 1999, a place she had visited before. She was identified from the club's records within hours, found not criminally responsible that October and committed to the Niuvanniemi state hospital at Kuopio. No motive was ever found.
Guadalupe Ronquillo-Ovalle is one of the five with no prosecution, because she is among the dead. Preliminary autopsies found that three children and Israel Alvarez died of homicidal gunshot wounds and that she died of a self-inflicted one, and the Navarro County sheriff's office continued to investigate it as a murder-suicide while awaiting DNA results.
Three more end with the killer dead and nothing that explains it. There was no prosecution in any of them. Mary Ann Holder shot five members of her family and wounded a man; the Guilford County sheriff confirmed in January 2012 that she had been the only shooter, on ballistics and mobile telephone records placing her at all three scenes, and she left two notes taking responsibility and giving no reason. The Dallas County Medical Examiner ruled Angelica Vazquez's case a murder-suicide, finding that she shot her husband and both children and then herself, and no motive was ever released. Michael Ryan killed sixteen people at Hungerford in 1987 and shot himself the same day; no motive was ever established, and the absence has been filled with speculation for nearly forty years.
What these nine entries have in common is a discipline rather than a mystery. Each one had the opportunity to offer a theory, a bad childhood, a diagnosis, a resentment, and declined, because nobody established one: not a court in the four that reached one, and not an investigation in the five that did not.
That is a harder thing to publish than it sounds. A serial murder case with no explanation is unsatisfying, and the pressure to supply one comes from every direction: the press at the time, the books afterwards, the reader now. Ryan's case has attracted four decades of it.
The entries here say no motive was ever established, and stop. Given how much of this archive's work has gone into removing invented detail, that sentence is doing more than admitting ignorance. It is refusing an invitation.