I have not read the papers showing that using a different font to sign something is a sign of fraud. DO share the citations! Seriously, no idea what the story is with this study, but the guy has an injury related serious disability with his hands, so he uses transcription software to type, and others in the office may copy edit his transcribed writing. I have used different devices or software to write documents too, and it makes the fonts different. Does that make me a fraud? Seriously, if you are that eager to prove someone is guilty that you come up with random "evidence" with no basis, it calls into question the rest of your arguments.