The Collaborative International Dictionary of English v.0.48:

Evidential \Ev`i*den"tial\, a.
   Relating to, or affording, evidence; indicative; especially,
   relating to the evidences of Christianity. --Bp. Fleetwood.
   "Evidential tracks." --Earle.. -- Ev`i*den"tial*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

evidential
    adj 1: serving as or based on evidence; "evidential signs of a
           forced entry"; "its evidentiary value" [syn:
           evidential, evidentiary]

Moby Thesaurus II by Grady Ward, 1.0:

101 Moby Thesaurus words for "evidential":
   Christophanic, Satanophanic, absolute, adducible, admissible,
   angelophanic, appearing, attestative, attestive, authentic,
   based on, certain, circumstantial, conclusive, connotative,
   convincing, cumulative, damning, decisive, demonstrating,
   demonstrative, denominative, denotative, designative,
   determinative, diagnostic, disclosive, displaying, documentary,
   documented, emblematic, epiphanic, evidentiary, evincive, ex parte,
   exhibitive, expositional, expository, expressive, eye-witness,
   factual, figural, figurative, final, firsthand, founded on,
   grounded on, hearsay, identifying, ideographic, idiosyncratic,
   implicative, implicit, incarnating, incarnational,
   incontrovertible, indicating, indicative, indicatory, indisputable,
   individual, irrefutable, irresistible, manifestative, material,
   materializing, meaningful, metaphorical, naming, nuncupative,
   overwhelming, pathognomonic, peculiar, pneumatophanic,
   presentational, presumptive, probative, promulgatory, reliable,
   representative, revelational, revelatory, semantic, semiotic,
   showing, signalizing, significant, significative, signifying,
   suggestive, sure, symbolic, symbolistic, symbological, symptomatic,
   symptomatologic, telling, theophanic, typical, valid, weighty