Trust, but verify.
— Former U.S. President Ronald Reagan
Ronald Reagan used the phrase in public, but he was not the first person known to use it. When Reagan used this phrase, he was usually discussing relations with the Soviet Union and he almost always presented it as a translation of the Russian proverb “doveryai, no proveryai”
The phrase is commonly used by TV actor David Caruso’s character Horatio Caine in CSI: Miami.