The Missing Manuscript

Famous author Professor Edwards' manuscript suddenly vanished from his study. He suspected one of his three assistants, named Anna, James, and Rachel, might be involved. Each assistant had a different task in the study when the manuscript disappeared.
Anna was responsible for organizing the professor's research notes and files.
James was tasked with proofreading and editing the manuscript draft.
Rachel's duty was to handle incoming correspondence and emails related to the professor's work.
Professor Edwards interviewed each assistant and got the following statements:
Anna: "I didn't take the manuscript. I was focused on organizing your research materials as usual."
James: "I have no idea about the missing manuscript. I was deep into editing and didn't leave my desk."
Rachel: "I swear I didn't take it. I was sorting through your emails and didn't touch the manuscript."
After examining their statements and considering their responsibilities, Professor Edwards quickly deduced who took the manuscript. Can you solve the mystery and identify the assistant who is guilty?

Solution: The thief is James. Professor Edwards realized this because James said he was editing the manuscript and didn't leave his desk, which meant he had direct access to the manuscript and could have easily taken it.