Verb (used with object), : Documents circumstantiated her evidence. ,He circumstantiated the accident.    From Dictionary.com. 

Nor is he more just, I think, against Tasso's Episodes, which he blames as not proper to circumstantiate his principal Action, not entring into the Causes and Effects thereof, but seeking too much to please, tho '.    From Wordnik.com.  [Epistle to a Friend Concerning Poetry (1700) and the Essay on Heroic Poetry (second edition, 1697)] Reference

We would have our eyes upon that too, so to circumstantiate all our duties, as they may have least offence in them, and be exposed to least obloquy of men, 1 Pet. ii.    From Wordnik.com.  [The Works of the Rev. Hugh Binning] Reference

In many cases, to which, from their circumstantiate nature, neither the written nor the consuetudinary law is directly appli - cable, these are the Responsa Prudentum which supply that un - avoidable deficiency.    From Wordnik.com.  [Peerage of England, genealogical, biographical, and historical] Reference

It may easily be imagined how the poor woman felt at this unexpected summons, and at the announcement, necessarily defective and confused, of an escaped but fearful danger, —an obscure event, which the messenger could neither circumstantiate nor explain, and of which she had not the slightest ground of explanation in her own previous thoughts.    From Wordnik.com.  [Chapter XXIV] Reference

"Wal, that's easy to circumstantiate.    From Wordnik.com.  [The Rifle Rangers] Reference