Secord wrote two accounts of her walk, the first in 1853, and the second in 1861. Neither account contains details that can be corroborated with military accounts of the battle, such as specific dates or details about troops. Her account changed throughout her life. Historian Pierre Berton noted that she never stated clearly how she learned of the impending attack. She told FitzGibbon that her husband had learned about it from an American officer, but years later told her granddaughter that she had overheard the plans directly from the American soldiers billeted in her home. Berton suggested that Secord's informant could have been an American still residing in the United States, who would have been charged with treason had Secord revealed her source. In the 1860s, as Secord's story gained prominence, historian William Foster Coffin added new details, which included the claim that Laura had brought a cow with her as an excuse to leave her home in case the American patrols questioned her.