McLEAN, Virginia: Colleagues of a historian accused of altering a presidential pardon signed by Abraham Lincoln to make it appear he had made a major discovery say he betrayed the trust that had been placed in him. The accused historian – Thomas P. Lowry, 78, of Virginia – denied Tuesday that he actually tampered with the document despite a written confession he gave to the National Archives earlier this month. The National Archives announced on Monday that Lowry used a fountain pen with special ink to change the date on a presidential pardon issued by Lincoln to a Union army deserter from April 14, 1864, to April 14, 1865. The date change made it look like the pardon was the last official act carried out by Lincoln before he was shot that night at Ford's Theatre by John Wilkes Booth. Archives officials say Lowry's purported discovery did vault him into prominence in the world of Abraham Lincoln historians when he announced his findings back in 1998. The Archives itself praised Lowry's work at the time as “a unique and substantial contribution to Lincoln research and to the study of the Civil War.” In a phone interview Tuesday, Lowry recanted his confession and said he offered repeated denials to Archives investigators over the course of a two-hour interview but eventually wore down when they refused to believe him. “I foolishly signed a statement saying I had done it,” Lowry said. “Now they're portraying me as a fool, a liar and a criminal. I screwed myself by signing it.” But the inspector general's office for the Archives says that not only did Lowry willingly confess, he offered up details about how he did it with a fountain pen and special ink. “He voluntarily provided a statement, written in his own hand, in which he elaborated on his actions and provided specific details on how he committed this act,” said Ross Weiland, the Archives' assistant inspector general for investigations. “He subsequently swore to the statement's accuracy and signed the statement. No threats, rewards, or promises of any kind were made to Mr. Lowry in return for his sworn statement.”