A more thorough explanation:

Definition: An exemplar is a typical or ideal example of something. It can also refer to non-testimonial identification evidence, such as fingerprints, voiceprints, and DNA samples.

• A painting by Van Gogh is considered an exemplar of post-impressionist art.
• The Declaration of Independence is an exemplar of a historical document that shaped the United States.
• Police may use a suspect's DNA as an exemplar to match against evidence found at a crime scene.

The first two examples illustrate how an exemplar can be a standard or ideal example of something. The painting by Van Gogh is a typical example of post-impressionist art, while the Declaration of Independence is an ideal example of a historical document that influenced the United States. The third example shows how an exemplar can be used as non-testimonial identification evidence in a criminal investigation.