THE FOUR TYPES OF EVIDENCE. There are four traditional types of evidence: real, demonstrative, documentary, and testimonial. Some rules of evidence apply to all four types and some apply only to some or one of them. First, we will cover general rules of admissibility that apply to all evidence. Then, we will cover foundational rules that relate to specific kinds of evidence. Finally, we will cover some special topics, like the form of examination, the hearsay rule, and the lay opinion rule, that frequently cause problems in the courtroom.