The morning of June 26, 1828, dawned bright and full of promise over southern Ireland’s Cork Harbor. Brawny longshoremen heaved crates to and fro with casual ease, chattering gulls swooped through the briny air, and a motley collection of vessels mingled amid rippling waters.

It was, at first glance, an utterly normal day at the docks.

William Scoresby, Jr., an Arctic explorer, scientist, and Anglican minister, surveyed the scene from a small boat ferrying him and his brother-in-law from Corkbeg Island to the town of Cobh, just across the harbor. He was interrupted from his own thoughts when another passenger gestured at an unremarkable brig anchored in the distance.

A crew had reportedly just been murdered on a ship, the man explained, and he believed it was that one.

The passengers erupted in surprise and shock, and all but one woman abandoned their plans to alight on the opposite shore. After dropping her off, they steered the boat straight toward the brig to investigate. The lone officer patrolling the deck obligingly confirmed that murder had indeed befallen the crew.

“It is too true,” he said, “and here they are, all lying dead!” He invited the party aboard and pointed them toward the skylight of the cabin. “Five swollen bodies, lashed on their backs, mangled with ghastly wounds and clotted with gore, were lying conspicuously visible beneath,” Scoresby recalled in his 1835 account Memorials of the Sea, “with the lower extremities of two others seen projecting from the mate’s cabin.”

It’s unclear why the officer saw fit to let strangers examine the bloodbath, though Scoresby’s ministerial status may have helped inspire trust—and his brother-in-law just happened to be the first magistrate on the scene. Whatever the case, the crimes immediately captivated Scoresby, and he didn’t squander his opportunity to find out more. Over the following weeks, he interrogated all the survivors, followed the trial with unerring attentiveness, and even struck up what became a years-long correspondence with the murderer himself.

Scoresby’s investigation centered on a simple question: What could possibly drive a well-respected, rational man to commit such heinous acts?

Whispers of Mutiny

A 19th-century captain, smelling something fishy.clu/iStock via Getty Images

The brig, Mary Russell, had sailed from County Cork to Barbados during the winter of 1827 under the command of Captain William Stewart, a trim 53-year-old with sharp features and a crop of red hair. After unloading their cargo of mules, the crew members packed the ship with sugar, animal hides, and other exports and prepared to return home. They picked up an unexpected passenger, too: Captain James Raynes, an Irishman who had recently been fired as first mate on another ship due to his newfound affinity for alcohol. Stewart had somewhat reluctantly agreed to let Raynes hitch a ride on the Russell, which set off on May 9, 1828.

Soon after their departure, Stewart dreamed that Raynes was plotting a mutiny. He took it as a warning sent from God. Stewart believed Raynes had reason to want to commandeer his ship. Not only was Raynes returning to Ireland in disgrace, but his chances of getting hired to captain another ship after earning a reputation as a drunkard seemed slim. “I suspected him, therefore, that he wanted to turn pirate,” Stewart later explained. And here was a valuable vessel for the taking, with only its captain in his way.

It wasn’t long before Stewart found evidence supporting his belief that Raynes was colluding with the crew. Raynes shaved in the crew’s compartment, for one, and chatted with them in Gaelic, which Stewart didn’t speak. One sailor, John Keating, even asked Stewart if he thought Raynes was a skilled navigator; another, John Howes, asked Stewart to teach him more about lunar distance—a key element of celestial navigation.

As the weeks went by, Stewart’s paranoia escalated. He ordered a few trusted crew members to sleep in his cabin for protection, and he kept an ax, a crowbar, and other weapons within reach. To prevent Raynes and his alleged co-conspirators from being able to sail the ship without him, he tossed logbooks, charts, and vital instruments overboard. During his nighttime watch on June 18, first mate William Smith trekked down to steerage three times for oil and more materials to help him fix a faulty lamp. This, too, Stewart found extremely suspicious, and the next morning he demanded that the men tie up the first mate.

“If we lash the mate without reason,” one pointed out, “he will take the law of us when we get home.” But after watching Stewart grow practically apoplectic over the refusal, the men convinced Smith that it would be in everyone’s best interest if he agreed to the restraints. “Here! Tie away!” Smith said, and was then confined to a cramped compartment under the cabin.

Unfortunately, this did little to assuage the captain’s anxiety. Fearing for his life, he hatched a grander scheme.

A Dutiful Crew, Deceived

An illustration of a 19th-century brig.duncan1890/iStock via Getty Images

On June 21, the Mary Russell’s sails stood taut against a clear sky as the ship cruised swiftly toward Cork. So when Captain Stewart instructed his crew to roll up a number of the sails, slowing their progress, they considered it an odd request. But they didn’t argue.

Except for Smith (still captive beneath the cabin), three young ship's apprentices, and a boy who’d come on the voyage to improve his health, all the ship’s crew spent the afternoon busy on deck. But every 15 or 20 minutes, Stewart or one of the apprentices showed up to summon one of the men to the cabin with some new request. They never returned to the deck. Soon, six men had disappeared, and only two—seaman John Howes and mule tender James Murley—remained.

One boy then came to fetch Howes, who got about halfway down the steps to the cabin before freezing abruptly on the spot: Stewart stood at the bottom, brandishing guns. Howes looked at him levelly and asked, unruffled, “What do you intend to do with your pistols?”

Stewart cried out that he knew all about their mutinous plot and demanded that Howes submit to being bound. Howes refused, fleeing to the deck as Stewart fired wildly at his retreating figure. But Howes ultimately decided that the best way to calm the captain was simply to abide by his wishes, and he and Murley both agreed to be tied up. Howes ended up on the half-deck, and Murley was taken to the cabin, where the other sailors already lay bound and defenseless.

After hours of insufferable discomfort, Howes soured on his earlier show of compliance and worked to loosen the ropes. When Stewart visited him the next morning, he immediately noticed how slack the lashings looked. A brawl ensued, during which Howes was shot three times—in his thumb, side, and thigh—and beaten by the teenage apprentices, whom Stewart had coaxed into submission by threatening to kill them and also promising “great pecuniary reward, sufficient to make them gentlemen.” Against all odds, Howes escaped with his life and hid among the cargo crates.

As Stewart revealed to Scoresby later, he hadn’t originally planned to harm anyone. He had asked the men to furl the sails so he could sail on without their help, in search of a ship to rescue him from their treachery. But one had already passed them by during the battle with Howes, and a second turned away—possibly thinking the Mary Russell was a pirate ship—despite Stewart’s attempts to flag it down.

And then a new thought struck him: Surely if the crew were innocent, God would have directed the second ship to rescue them. And since death was, in Stewart’s understanding, a punishment befitting the crime of mutiny, that must be what God intended for them. That notion, together with the terror that Howes, still at large, could murder him at any moment, gave way to a sudden, sobering realization.

Stewart must kill his crew.

Carnage in the Cabin

A captain spies a ship in distress.clu/iStock via Getty Image

Crowbar in hand, he barged into the cabin and bellowed, “The curse of God is upon you all!” Before his prisoners had time to register those words, Stewart began to bludgeon them to death, one by one—second mate William Swanson, James Murley, carpenter John Cramer, seaman Francis Sullivan, seaman John Keating, mule handler Timothy Connell, and James Raynes. He then threw down his crowbar, seized an ax, and methodically hacked through each man to ensure none survived.

The three apprentices, who ranged in age from 10 to 15, watched in horror as the blood streamed through a hole in the cabin floor onto first mate William Smith, still immobilized below. Stewart widened the hole with his ax and battered Smith with blows from both the crowbar and a harpoon. After feeling Smith’s cold neck to confirm he was dead, the captain sat back, relaxed at last.

Stewart commanded the boys to fetch him meat and alcohol, which he consumed right above the bloodbath. He finished the meal off with a smoke of his pipe, and even commented that he “thought no more of the bodies before him, than if they were a parcel of dead dogs.” As he confessed later, Stewart felt that he’d not only saved his own life, but also the Mary Russell and all the profits its owners would earn from the cargo. The loss of the crew members—who, again, Stewart believed were destined for death—must have seemed to him like a reasonable price to pay.

So when Stewart successfully hailed the next passing vessel, the Mary Stubbs, he wasn’t worried about consequences for his crimes. In fact, he went so far as to ask the captain, Robert Callendar, whether he “were not a valiant little fellow to kill so many men?” Callendar and his men helped Stewart locate Howes. Smith was with him. “I now believe you were innocent,” Stewart told him. “I am sorry for having hurt you; it was God [who] spared your life!” In reality, Smith had some cargo to thank for his life. During Stewart's attack, he had shifted sideways slightly so that the harpoon stabs hit a pile of animal hides beside him. Stewart, whose view was likely obstructed by the splintered edges of the hole, mistook the animal skins for Smith's skin.

Howes and Smith were taken to the Mary Stubbs, and a few of Callendar’s men stayed behind to help sail the Mary Russell. Soon, however, Stewart’s paranoia returned, and he began to fear that the sailors were plotting to kill him. Twice he threw himself overboard, and twice they pulled him back on deck. They then moved him to the Mary Stubbs, where he jumped overboard once again. This time, he was picked up by a nearby fishing boat, which sped off.

The Captain on Trial

A crowded 19th-century courtroom.ilbusca/iStock via Getty Images

The Mary Russell and the Mary Stubbs arrived in Cork Harbor around midnight on June 25, and the murders were promptly reported to the authorities. A manhunt proved unnecessary—the fishing boat had delivered Stewart right to the Coast Guard, and he’d recounted his whole story in damning detail. Soon after they’d deposited him at a local jail in County Cork, the coroner called together a grand jury to determine the charges.

It wasn’t easy. Stewart’s homicidal spree clashed with a lifetime of level-headedness, and nothing suggested that his crew had actually planned a revolt. Though it seemed apparent that he was suffering from some sort of mental illness, jury members were in the dark about what it might be—and how it should factor into a legal ruling. On August 4, they charged him with murder, but specified that he was “in a state of mental derangement” at the time. It would be up to the prosecution and defense teams to decide how to spin that diagnosis to their advantage.

The trial commenced a week later in a courtroom packed with curious spectators, all jockeying for a glimpse of the alleged mass murderer. Stewart looked staid and respectable in his white waistcoat, black coat, and cravat. Silence fell over the room as the prosecutor launched into his opening statement, which focused on the relationship between insanity and innocence.

“Derangement of mind is not considered a sufficient excuse, unless the party is totally incapable of distinguishing between right and wrong,” he explained. If Stewart were totally incapable of knowing the difference, he should be found not guilty by reason of insanity. But it was up to the defense team to convince the jury that Stewart had been insane at the time—the prosecution was just aiming to prove that he had actually committed the murders.

As long as the jury validated the plea of insanity, Stewart should get a not guilty verdict. That wouldn’t, however, mean he'd be free. Much like how today’s defendants found not guilty by reason of insanity are often committed to psychiatric institutions, Stewart would be incarcerated in an asylum or even prison.

The trial proceeded as a jumble of witnesses describing the events on the Mary Russell and doctors weighing in on Stewart’s mental condition—not unlike a modern-day trial, though early 19th-century psychiatry was a far cry from what it is today. One medical professional testified that Stewart must have been suffering from monomania, where a person “might be perfectly sane on all other subjects, but a particular one.” For Stewart, that purported subject was the possibility of a mutiny.

As for what caused insanity, the judge explained that it was part of God’s divine plan. “The question, therefore, is, whether he acted deliberately by the instigation of the Devil, or whether he acted under the visitation of God which impaired his senses,” the judge told the jury. “When it pleases God to deprive a man of his understanding, it belongs not to any human tribunal to bring that man to punishment.” For that reason, the jury should understand that 'guilty' and 'insane' were mutually exclusive.

But his message apparently wasn't quite clear enough. After deliberating for roughly an hour and a half, the jury came back with a guilty verdict and a confirmation that Stewart had indeed been insane at the time. The judge, having just explained that nobody could be guilty and insane, told them the court couldn't accept the verdict. “The verdict is actually tantamount to 'not guilty;' for the law does not recognize that as guilt,” an assistant judge chimed in. “You can amend it without leaving the box.” So the jury did, finding Stewart insane but not guilty, and the judge sentenced Stewart to “close confinement during life, or during his Majesty’s pleasure.”

Stewart sunk to his knees and clasped his hands together in prayer. “I have great reason to bless God,” he declared, “for if I had committed the murder willfully, I would not have wished to live myself—but I did not!”

Landlocked for Life

Cork's City Gaol, now a museum.Arsty/iStock via Getty Images

Stewart spent the rest of his life in confinement: in Cork's city jail until 1830; Cork Lunatic Asylum until 1851; and Dundrum Asylum for the Criminally Insane until his death, at age 98, in 1873. He passed the years tutoring his children, making model boats to bring in some income for his family, and studying the Bible. When William Scoresby visited him in August 1829, Stewart expressed no wish for freedom. “If I should be released,” he said, “everyone would point to me, and say, ‘There goes that miserable man who killed his sailors!’”

But lifelong captivity provoked bouts of anxiety and depression in Stewart, and he vacillated between calm resignation and vehement attestations of his innocence. While he struggled to understand his mental illness, Stewart took solace in the knowledge that God was behind it—a belief that Scoresby, the judge, and the rest of pious Ireland echoed.

“Surely the dreadful carnage was permitted by the Providence of Heaven, because their hour was come,” Scoresby wrote. “Yet it was a mysterious, as well as a dreadful, visitation, and we must speak of ‘the might of God’s terrible acts’ with humility and reverence.”

Of course, Stewart’s trial would have gone down differently had it happened in present-day Ireland. God wouldn’t have featured so heavily—nor would terms like mental derangement—and Stewart would have received more advanced psychiatric treatment and perhaps a more accurate diagnosis than monomania. But the verdict, as confirmed by a 2006 law, could very well have been the same: “Not guilty by reason of insanity.”