'unknown subjects' is a correct and usable phrase in written English.
You can use it when referring to a group of people or things that are unfamiliar or unidentified. For example, "Most of the scientific studies of this phenomena have been conducted using unknown subjects."
Attempts were made to identify the unknown subjects utilizing IDIS.
Though the book drips with celebrity, some of its most arresting images are of unknown subjects.
A statement issued by police with the sketches on Saturday said Stone "was in the area of 21st Street and K Street when a physical altercation ensued with a group of unknown subjects".
Working from black-and-white studio photographs of both his family and unknown subjects from the 1900's to the 1940's, he creates representations of African-Americans that teeter between prideful or strong-willed, and distracted or careworn.
On TV, Gubler is best known for playing Spencer Reid, a brilliant member of an elite FBI behavioral analysis team, tracking down unknown subjects — or "unsubs" — for 14 seasons.
That seemed to be the lesson of Warhol's "Screen Tests," his four-minute 16-millimeter film portraits of famous, semi-famous and unknown subjects.
Last week, Mr. Ashcroft had identified Mr. Jiddi only as an unknown subject.
For the moment, he is known in law enforcement jargon only as Unsub, or unknown subject.
It was like one of those bad dreams, when you are about to take an examination in an unknown subject after cutting classes all semester.
The oil, 31.5 by 24.5 inches, was acquired by the art gallery 70 years ago as a portrait of an unknown subject and was only recently restored.
Out of that insight came another prediction: "One of the things we began saying in some of our profiles was that the UNSUB" — the unknown subject — "would drive a policelike vehicle, say a Ford Crown Victoria or Chevrolet Caprice".
