What is an example of biological evidence at a crime scene?

Biological evidence is identified by its connection to living organisms and can provide critical information in criminal investigations. Blood, saliva, or hair fits this definition perfectly as these materials originate from biological sources—humans or other animals. They hold significant evidential value because they can often be analyzed through DNA testing, which helps in identifying suspects or linking individuals to crime scenes.

In contrast, glass shards are classified as physical evidence, while cigarette butts, although they may contain trace biological materials like saliva, primarily represent personal property or specific behaviors related to an individual. Footprints, whether left by human or animal, are considered impression evidence and are used to determine movement or presence at a scene but do not involve biological material in the same way. Therefore, blood, saliva, or hair stands out as clear examples of biological evidence critical for forensic analysis.