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U.S. President Abraham Lincoln pardoned a soldier in the Civil War, and in 1998 that document was re-discovered. But "It was the date that made the document significant," writes Ars Technica: April 14, 1865, "meaning the pardon was likely one of the last official acts of President Lincoln, since he was assassinated later that same day at Ford's Theater in Washington, D.C. The pardon was broadly interpreted as evidence for a historical narrative about the president's compassionate nature: i.e., his last act was one of mercy." But now scientists at America's National Archives have conducted a new analysis (published in the journal Forensic Science International: Synergy), and "confirmed that the date was indeed forged (although the pardon is genuine)." An archivist named Trevor Plante became suspicious of the document, noting that the ink on the "5" in "1865" was noticeably darker. It also seemed as if another number was written underneath it. Then Plante consulted a seminal collection of Lincoln's writings from the 1950s. The pardon was there, but it was dated April 14, 1864 — a full year before Lincoln was assassinated by John Wilkes Booth. Clearly the document had been altered sometime between the 1950s and 1998 to make the pardon more historically significant.. Investigators naturally turned to the man who made the discovery for further information. They began corresponding with Thomas Lowry [a retired psychiatrist turned amateur historian] in 2010. Initially, Lowry seemed cooperative, but when he learned about the nature of the investigation, he stopped communicating with the Office of the Inspector General, thereby arousing suspicion. So the investigators knocked on the historian's door one January morning in 2011 for an interview. Shortly thereafter, the National Archives released a statement that Lowry had confessed to altering the date on the pardon. Lowry confessed to bringing a fountain pen into the research room, along with fade proof, pigment-based ink, and changing the "4" in "1864" to a "5." Lowry couldn't be charged with any crime because the statute of limitations for tampering with government property had run out, but he was barred from the National Archives for life. But there's a twist: Lowry soon recanted, claiming he had signed the confession under duress from the National Archives investigators... Long-time Slashdot reader waspleg writes that Ars Technica "goes through the analysis of how it was verified to be a forgery using several techniques," including ultraviolet light and X-ray fluorescence analysis to study chemicals in the ink. From the article: An examination under magnification and reflective fiber optic lighting showed the ink used to write the "5" was indeed different in overall color compared to the other numbers in the date. Furthermore, "Vestiges of ink from a scratched away number can be seen below and beside the darker '5,' as well as smeared across the paper," the authors wrote. Additional analysis under raking light — a technique that accentuates hills and valleys in the paper texture — revealed abrasions to the paper under and around the "5" that were not observed anywhere else on the document. The team also determined that the paper around the "5" is thinner than everywhere else, and that ink residue of the scratched-away "4" were caught in the abraded paper fibers, clearly visible using transmitted light microscopy... "The authors also concluded that there is no way to restore the document to its original state without causing further damage."