Both Uses

circumstantial evidence
in
The Hunt for Red October
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"I do not claim that this story is true, nor do I claim it is even a likely one at this point," Gerasimov said, keeping his voice detached and clinical, "but there is sufficient circumstantial evidence supporting it that I must recommend an in-depth investigation by the Committee for State Security touching on all aspects of this affair."†
Chpt 15.

circumstantial evidence = evidence that can suggest something, but does not prove it
On the other hand, they can believe the story we planted through Henderson, which is also unattractive but is supported by a good deal of circumstantial evidence, especially our efforts to entice their crewmen to defect.†
Chpt 16. *

Definitions:

(1) (circumstantial evidence)
evidence that can suggest something, but does not prove it

For example, if someone’s fingerprints are on a window that was broken during a burglary, that can suggest they were there. But it doesn’t prove they broke in—maybe they touched the window earlier for an innocent reason.
(2) (meaning too rare to warrant focus)