PARIS - Depending on what you read, Maximilien de Robespierre was a defender of the poor and downtrodden — “the Incorruptible” who defended the values of the French Revolution to the end.

Or he was a monster who slaughtered thousands for revolutionary crimes, a lawyer who opened up the path of legalised terror later trod by Hitler and Stalin.

Now, with the help of 21st-century tools, forensic scientists are providing insights into a figure who left such a deep but contested imprint on history.

Robespierre, they say, probably suffered from a crippling auto-immune disorder called sarcoidosis — a disease that may have played an indirect role in his downfall. In 1794, the ultra-radical would have been severely weakened when his terrified foes mustered the courage to rush him to the guillotine, they say.

“He was killed by the guillotine but he was already exhausted by the political battle, his insomnia and his own frenetic personality,” said Philippe Charlier, one of Europe’s leading forensic anthropologists.

“But he was also weakened by this disease, which debilitates and tires the body,” Charlier said in a phone interview with AFP. In sarcoidosis, the immune system goes haywire and attacks the body’s own tissues. Its signature is patches of reddened, swollen tissue called granulomas, but the inflammation also causes knock-on problems in organ functions.

Charlier, of the University of Versailles, and Philippe Froesch of the Parc Audiovisual de Catalunya in Barcelona, write up their conclusions in a letter to The Lancet medical journal, published on Friday.

Death mask clue. They build the diagnosis on a reconstruction of Robespierre’s face, contemporary portraits, a death mask made by Madame Tussaud — now known for the famous waxworks museum in London — and eyewitness accounts.

The list of known symptoms is long: vision difficulties; nose bleeds so extreme “he covered his pillow with fresh blood each night”; yellow skin, a sign of jaundice; suppurating leg ulcers; and permanent twitching of the eyes and mouth.