A dead woman could still sign deeds, receive monies, travel to Lyon, and convey instructions to her husband, provided a living man took charge of her affairs. Antoine-François Derues carried this convenient fiction to its ultimate conclusion. Madame de La Motte had vanished; he explained that she had received the purchase price for her estate and fled. Notarized instruments stood ready to corroborate his assertions. Thus, on parchment, an ancestral estate changed hands, while the vendor lay beneath the flagstones of a Parisian cellar and her son was consigned to the earth at Versailles under an assumed name.
The affair of 1777 commenced with an appetite for landed property. An established grocer in Paris, Derues had entered into negotiations with Monsieur and Madame de La Motte to acquire the estate of Buisson-Souef. The initial covenant dated back to December 1775. Yet to purchase required payment, and the merchant possessed none of the resources he so lavishly promised. In the chasm between the craving for ownership and the reality of his coffers, he cultivated that fertile terrain where swindlers lodge their assurances: tomorrow, a remittance; soon, a windfall of inheritance; after the next signature, all would be discharged. The owners, however, awaited coin, not narratives. Madame de La Motte duly came to Paris to conclude the transaction.
She arrived in the capital with her son and was lodged under Derues’s own roof. This hospitality is pivotal to the anatomy of the crime. It placed the creditor beneath the debtor’s rafters, at his board, delivered into the presence of whatever beverages or restorative draughts he might set before her. The son was subsequently placed in an academy. Toward the close of January 1777, the mother fell gravely ill. The sentence of the court, as preserved in period accounts, attributed her death to poison administered by Derues. It noted, moreover, the dismissal of the servant and the careful stratagems devised to keep inquisitive callers at bay. An intimacy offered as a benevolence became the very instrument of the victim’s isolation.
Madame de La Motte expired during the night of January 31st. Derues made no lawful declaration of her decease. The corpse was shut within a trunk and conveyed to the Rue de la Mortellerie, into a cellar leased under the assumed name of Ducoudray. There it was concealed. This change of name did not merely serve to throw a curious observer off the scent; it severed two enterprises that the judicial inquiry would later be forced to reunite: on the one hand, the merchant negotiating an estate; on the other, a cellar tenant whose comings and goings might pass for those of any tradesman warehousing goods.
There remained the son. Derues persuaded the boy that his mother was residing at Versailles and desired his presence. The youth thus followed the very man who had just made away with her. Lodged in the house of a cooper, the boy fell ill in his turn. The judicial findings record the potions and mixtures administered by Derues, as well as his obstinate refusal to summon a physician despite the worsening condition of his charge. He died on February 15th. On the morrow, Derues had him interred under the name of Beaupré, presenting him as his nephew. The falsehood now crossed the threshold into the parish register: it was no longer content merely to circulate from mouth to mouth.
While the two victims were thus blotted from the sight of the living, their purported signatures and post-mortem desires continued to labor on paper. An act dated February acknowledged the receipt of one hundred thousand livres and amended previous covenants. Another instrument was devised to suggest a financial transaction capable of lending color to so massive a disbursement. In March, an errand undertaken in Lyon produced yet another outward token of Madame de La Motte’s continued existence. The trial record requires no adherence to the picturesque accounts of the disguises Derues allegedly assumed. What the verdict established was the calculated employment of forged instruments to bolster an imaginary settlement.
To the bereaved husband, Derues proffered a tale far crueler than mere absence: his wife, he averred, had absconded with the gold in the company of a stranger. Thus was the disappearance converted into the disgrace of the departed. He relied upon the embarrassment, the shame, and the hesitation of a man informed that he had been betrayed. The contrivance possesses a singular venom: it compels one searching for a loved one to begin by defending her honor. Monsieur de La Motte did not falter. The grocer’s explanations were challenged, his movements scrutinized, and the notarial acts confronted with the very circumstances they pretended to certify.
The magistrates’ inquest ultimately breached the cellar. It was no longer a matter of awaiting a letter, debating a journey, or being led astray toward a fresh address. In that subterranean vault, the missing woman was to reclaim her name. The hiding place yielded up its damning proof: the body of Madame de La Motte was disinterred from the premises rented under the borrowed identity. At Versailles, the youth’s burial was likewise reunited with his true lineage. The two corpses converged at last within the same proceeding. The instruments that had kept them seemingly alive or transformed their names were unmasked as the apparatus of an assassination.
The Châtelet condemned Derues on April 30, 1777. The sentence was affirmed by the Parlement of Paris in early May. Its scope reached far beyond the mere act of poisoning: it addressed the forgeries, the counterfeit receipt, the machinations undertaken to usurp the title of the estate, and the calumnies spread against the victim. The decree likewise ordered that the son’s death register be rectified. This administrative injunction remains one of the most striking features of the cause. Following such an accumulation of documents wrought to deceive, a parish ledger was commanded to restore to a dead boy his true name, so that his father and the rightful parties might assert their legal rights.
Derues persisted in denying the poison. He was subjected to the question extraordinary prior to his execution, as required by the jurisprudence of the age to discover potential accomplices. He maintained this denial unto his final hours. After such an architecture of explanations designed to divert suspicion, nothing remained to him but the obstinate refusal to confess the venom. His judges had ruled; his word could no longer arrest his progress toward the scaffold. On May 6th, he was conducted to the Place de Grève, broken upon the wheel, and his body cast into the flames.
Surviving period engravings depict the various stages of this execution, attesting to the brisk commerce that instantly fed upon the event. The petty merchant who had coveted a seigneurial domain became a notorious figure, destined for street ballads and chronicles of villainy. Yet the estate of Buisson-Souef had never been purchased with the sums inscribed upon the parchments. It had been pursued at the cost of two lives, then buttressed by a scaffolding of forgeries. The law had been forced to dismantle this edifice sheet by sheet, to uncover a cellar, a grave, a stolen identity. It had not merely brought a poisoner to justice: it had prevented a man from legally possessing what he had sought to acquire by slaughtering those to whom it was owed.