“The novel tells the story of Valentine Michael Smith, a human who comes to Earth in early adulthood after being born on the planet Mars and raised by Martians. The novel explores his interaction with — and eventual transformation of — terrestrial culture.”
“Several later editions of the book have promoted it as “the most famous science fiction novel ever written”. While initially a success among science fiction readers, over the following years word-of-mouth caused sales to build, requiring numerous subsequent printings after the first edition. Eventually Stranger in a Strange Land became a cult classic.”
“A fair witness is a fictional profession invented for the novel. A fair witness is an individual trained to observe events and report exactly what he or she sees and hears, making no extrapolations or assumptions. A photographic memory is a prerequisite for the job, although this may be attainable with suitable training.”
“In Heinlein’s society, a fair witness is an absolutely reputable source of information. By custom, a fair witness acting professionally, generally wearing distinctive white robes, is never addressed directly, and is never acknowledged by anyone present.”
“A fair witness is prohibited from drawing conclusions about what they observe. For example, a character in the book is asked to describe the color of a house seen in the distance. The character responds, “It’s white on this side”; whereupon it is explained that one would not assume knowledge of the color of the other sides of the house without being able to see them. Furthermore, after observing another side of the house one should not then assume that any previously seen side was still the same color as last reported, even if only minutes before.”
I found this on FAIR WITNESS: Street Photography for the 21st Century. The attributed Wikipedia but I couldn’t find this description there.