In a couple of books and articles I've come across an adage, “the first liar is always believed most”:
Now, I talked to the captain first, but I want you to know that great old saying, “The first liar gets believed”, does not apply with me. I listen to everybody the same.
—Poyer, David. The Gulf, p. 322.*And while I agree the digital age gives you additional options for setting the record straight or refuting allegations, there’s another old adage I heard once that seems to be true as well: “the first liar is always believed most.”
—Barrett, John. Comment section, “Is It a Better Time Than Ever to Pick Fights With the Press?”, Mr. Media Training Blog.
Where did this originate?
* Quotation verified using Amazon’s search inside this book feature, search text [ first liar ].