Most of what I read is history (I am currently reading a biography of Louis XIV). People who read or study or write history will sometimes come to a point where no one knows for certain if something happened or not. I read a book that alleged that Napoleon was poisoned to death on St. Helena. Maybe he was. But maybe wasn’t. Sometimes, the end of the road is just a “maybe”. The Thomas Jefferson/Sally Hemmings story is just such a “maybe”. It is wrong IMO to stretch a “maybe” into a “known fact”.
He was. Napoleon used to give away locks of his hair as "gifts" and upon his death, more locks of hair were taken.
Researchers contacted the people who had these samples of Napoleon's hair and the dates they were taken, and they analyzed these hair with a mass spectrometer. They found increasing levels of arsenic rising to fatal levels just prior to his death.
Doctors also examined his described symptoms which were recorded at the time, and all his symptoms were consistent with arsenic poisoning. Further evidence is had in the fact that when his body was moved after having been buried for quite some time, it was in perfect condition with no signs of decay, as if he had died the day before.
This is also a characteristic of heavy arsenic poisoning because when arsenic gets into the cells of human tissue it kills bacteria that tries to consume the tissue.