The verifier was a peace of technology developed by scientists from the Terran Federation. It was basically a very advanced lie detector.
Unlike earlier attempts to produce a reliable means of determining truthfulness, the verifier used the brain waves of the individual being questioned. Under Federation law, verifiers could not be used without an explicit court order, and even then, there were stringent safeguards, limitations on the questions which could be asked, to prevent "fishing" expeditions.
The verifier was in use for almost a century, during which no instance of one of the devices reporting a knowing lie as the truth was been reported, but it could only tell an interrogator whether or not the person questioned was telling the truth as he or she knew it.
Certain mental disorders could return contradictory readings.
The Stone of Schueler Edit
A verifier disguised as a blue crystal was entrusted to the Wylsynn family some centuries before Merlin Athrawes arrived in the Kingdom of Charis. Known as the Stone of Schueler, it was passed on from generation to generation until it served Paityr Wylsynn in finding out if the Charisian leadership's intentions were true and just. (OAR)