The Collaborative International Dictionary of English v.0.48:

Proven \Prov"en\, p. p. or a.
   Proved. "Accusations firmly proven in his mind." --Thackeray.
   [1913 Webster]

         Of this which was the principal charge, and was
         generally believed to beproven, he was acquitted.
                                                  --Jowett
                                                  (Thucyd. ).
   [1913 Webster]

   Not proven (Scots Law), a verdict of a jury that the guilt
      of the accused is not made out, though not disproved.
      --Mozley & W.
      [1913 Webster]

WordNet (r) 3.0 (2006):

proven
    adj 1: established beyond doubt; "a proven liar"; "a Soviet
           leader of proven shrewdness" [syn: proved, proven]
           [ant: unproved, unproven]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "proven":
   ascertained, attested, authenticated, borne out, certified,
   circumstantiated, confirmed, corroborated, demonstrated,
   dependable, determined, established, faithworthy, fixed,
   incorruptible, inviolable, proved, reliable, responsible, settled,
   shown, straight, substantiated, sure, tested, to be trusted, tried,
   tried and true, true, trustable, trustworthy, trusty, unfalse,
   unperfidious, untreacherous, validated, verified