Define
The first voice on the page is a customer's. Proof arrives before the company's claim.
Mechanism
Borrowed voice. The lead sentence is already someone else's verdict. The seller speaks second.
Verdict
The result is easier to believe from a peer than from the brand, and the named person resembles the reader.
Don't
We only have vague praise, or the witness is famous in a way that belongs under celebrity endorsement.
Copy skeleton
"[QUOTE: specific result + timeframe]" · [NAME], [ROLE / CONTEXT] [1 line on why that result matters] [How the offer produced it] [ASK]
Gulf note
Name, city, and a number beat a glowing adjective. Gulf buyers ask who said it. If we cannot say, it is not this pattern.
Rights-cleared examples
How "Reason-Why" Copy Dried Up a County
Printers' Ink, Nov 28, 1906 (Vol. 57, No. 9): John E. Kennedy on the Snider canned bean campaign
Unigrid: A Brief History