Mathieu Dreyfus

His father, the director of a cotton factory, chose to retain French nationality for himself and his young children, and moved the family to Paris.

Mathieu arranged a meeting with Armand du Paty de Clam, the commandant who had carried out his brother's arrest.

On December 13, 1894, several days before Alfred's appearance before the Council of War, Mathieu attempted to meet with Colonel Jean Sandherr, the head of the intelligence service and a fellow Mulhousien.

Paty de Clam briefly suspected him of having written the bordereau, the main piece of evidence used to convict Alfred.

For his part, Alphonse Bertillon, called to verify the incriminating evidence, claimed that Captain Dreyfus had imitated the handwriting of his brother Mathieu to hide his own.

In February 1895, just after his brother's deportation, Mathieu met the Jewish anarchist journalist Bernard Lazare, who had just published Antisemitism, its History and Causes.

During the summer of 1895, Mathieu gave him all the documents necessary to compose the first exposé dedicated to the affair, which inspired Zola to write his article J'Accuse…!.

In 1896, Mathieu tried to reignite public interest in the case by having the English newspaper The Daily Chronicle print a false story claiming that his brother had escaped from his prison on Devil's Island.

It was quickly refuted, but still frightened the French authorities into restricting the conditions of Alfred's detention to prevent any escape attempt.

At the start of November 1897, Mathieu finally received confirmation that commandant Ferdinand Walsin Esterhazy was the true author of the bordereau attributed to his brother.

At Esterhazy's appearance on January 10, 1898, the president of the Council of War refused to question Mathieu and Lucie Dreyfus.

Supported by Bernard Lazare, Joseph Reinach, and Auguste Scheurer-Kestner, Mathieu persevered in convincing writers, scientists, and politicians that his brother was the victim of a miscarriage of justice.

After a retrial at Rennes, on September 9, 1899, Alfred Dreyfus was condemned to 10 years' detention, however the court noted extenuating circumstances.