urse no one can be
called to testify to it,--is it wholly unsusceptible of legal proof?
Experience has shown that circumstantial evidence may be offered in such
a case; that is, that a body of facts may be proved of so conclusive a
character, as to warrant a firm belief of the fact, quite as strong and
certain as that on which discreet men are accustomed to act in relation
to their most important concerns....

Each of these modes of proof has its advantages and disadvantages; it is
not easy to compare their relative value. The advantage of positive
evidence is, that you have the direct testimony of a witness to the fact
to be proved, who, if he speaks the truth, saw it done; and the only
question is, whether he is entitled to belief. The disadvantage is, that
the witness may be false and corrupt, and the case may not afford the
means of detecting his falsehood.

But in a case of circumstantial evidence where no witness can testify
directly to the fact to be proved, you arrive at it by a series of other
facts, which by experience we have found so associated with the fact in
question, as in the relation of cause and effect, that they lead to a
satisfactory and certain conclusion; as when footprints are discovered
after a recent snow, it is certain that some animated being has passed
over the snow since it fell; and, from the form and number of the
footprints, it can be determined with equal certainty, whether it was a
man, a bird, or a quadruped. Circumstantial evidence, therefore, is
founded on experience and observed facts and coincidences, establishing
a connection between the known and proved facts and the fact sought to
be proved.[15]

Under the head of direct evidence, as I shall use the term, would fall
the evidence of material objects: in an accident case, for example, the
scar of a wound may be shown to the jury; or where the making of a park
is urged on a city government, the city council may be taken out to see
the land which it is proposed to take. Though such evidence is not
testimony, it is direct evidence, for it is not based on reasoning and
inference.

29. Direct Evidence. Direct evidence is the testimony of persons
who know about the fact from their own observation: such is the
testimony of the witnesses to a will that they saw the testator sign it,
the testimony of an explorer that there are tribes of pygmies in Africa,
the testimony of a chemist to the constituents of a given alloy, or of a
doctor