2. _Witnesses must testify of their own knowledge_. Usually they are
barred from telling what they simply believe to be the fact or what they
have learned from hearsay.

3. _Evidence must go to prove the material allegations of the pleadings_.
It must be confined to the question at issue. It is to be observed that
the evidence must not only go to prove the matter alleged, but it must be
the _material_ not the superfluous matter. What is material and what
superfluous will depend upon the case. Thus if it is alleged that a suit
of clothes was obtained by the defendant at a certain time, his obtaining
the clothes is the material fact and the time may be superfluous or
immaterial. But if a note is in controversy its date is material as
establishing its identity.

4. _"The evidence must be the best of which the case is susceptible."_
Thus, in case of a written instrument the best evidence is the instrument
itself; the next best, a copy of it; the next, oral statement of its
contents. And a copy will not be accepted if the original can be produced.

5. _The burden of proof lies on the affirmative_. In civil cases the party
affirming is usually the plaintiff. In criminal cases it is the state.
Harmonizing with this principle is the constitutional provision that in
criminal cases the accused shall not be required to give evidence against
himself.

These are the principal rules of evidence, but they have many
applications. Learned volumes have been written elaborating them.

Grand Jury.--A grand jury may be defined as a body of men returned at
stated periods from the citizens of the county, before a court of
competent jurisdiction, chosen by lot, and sworn to inquire of public
offenses committed or triable in the county.

The number of grand jurors was formerly twenty-three. By statute many of
the states have fixed upon a smaller number, Oregon having only seven. A
common number is fifteen. Some states have no grand jury. In some others
the grand jury is summoned only when requested by the court.

The United States constitution and most of the State constitutions declare
that no person shall be held to answer for a criminal offense, except a
minor one, "unless on the presentment or indictment of a grand jury." This
is to save people from the vexation and expense of arrest and trial unless
there is reasonable presumption of their guilt. On the other hand, a grand
jury should aid in bringing to justice persons who indulge