The Collaborative International Dictionary of English v.0.48:

Indicia \In*di"ci*a\, n. pl. [L., pl. of indicium, fr. index an
   index.] (Law)
   Discriminating marks; signs; tokens; indications;
   appearances. --Burrill.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

INDICIA, civil law. Signs, marks. Example: in replevin, the chattel must
possess indicia, or earmarks, by which it can be distinguished from all
others of the same description. 4 Bouv. Inst. n. 3556. This term is very
nearly synonymous with the common law phrase, "circumstantial evidence." It
was used to designate the facts giving rise to the indirect inference,
rather than the inference itself; as, for example, the possession of goods
recently stolen, vicinity to the scene of the crime, sudden change in
circumstances or conduct, &c. Mascardus, de Prob. lib. 1, quaest. 15; Dall.
Dict. Competence Criminelle, 92, 415; Morin, Dict. du Droit Criminal, mots
Accusation, Chambre du Conseil.
     2. Indicia may be defined to be conjectures, which result from
circumstances not absolutely necessary and certain, but merely probable, and
which may turn out not to be true, though they have the appearance of truth.
Denisart, mot Indices. See Best on Pres. 13, note f.
     3. However numerous indicia may be, they only show that a thing may be,
not that it has been. An indicium, can have effect only when a connexion is
essentially necessary with the principal. Effects are known by their causes,
but only when the effects can arise only from the causes to which they. are
attributed. When several causes may have produced one and the same effect,
it is, therefore, unreasonable to attribute it to any one of such causes. A
combination of circumstances sometimes conspire against an innocent person,
and, like mute witnesses, depose against him. There is danger in such cases,
that a jury may be misled; their minds prejudiced, their indignation unduly
excited, or their zeal seduced. Under impressions thus produced, they may
forget their true relation to the accused, and condemn a man whom they would
have acquitted had they required that proof and certainty which the law
demands. See D'Aguesseau, Oeuvres, vol. xiii. p. 243. See Circumstances.