This will usually exclude children below a certain age, insane persons and persons drunk at the time of offering testimony.
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.