Module 2
Overview of the Criminal Justice System

Types of Witnesses

There are two types of witnesses:

Fact Witness or Lay Witness: Someone with personal knowledge relating to the case. Subject to the rules of evidence, a fact/lay witness can testify to events they observed and experienced firsthand but may not express any opinions they hold. Generally, what the person experienced with their own five senses.

Expert Witness: Someone with an expertise or specialized knowledge — as established by their education, training, skill, or experience — in a particular subject relevant to the case and beyond the knowledge of the average person. An expert witness can provide such specialized knowledge to assist the fact-finder in evaluating the evidence and can testify in the form of an opinion. Expert witnesses do not have to have any firsthand knowledge of the specific crime itself. For example, a DNA expert may be called to explain what DNA is, how DNA can be recovered from objects, and the science behind how DNA samples are analyzed. Module 5 provides more detail about expert witnesses in sexual assault trials, specifically how sexual assault forensic/nurse examiners can provide expert testimony.

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