Heinlein’s “fair witness” – more sci-fi related to Your Life, Uploaded

In Heinlein’s Stranger in a Strange Land, we find characters with photographic memories, who play the role of observers. The description at Wikipedia:

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. An eidetic memory is a prerequisite for the job, …

As a bonus, Heinlein also coins the word “grok” :)