Which of the following is an example of physical evidence?

Physical evidence refers to tangible items that can be collected and analyzed in a criminal investigation. DNA samples fall into this category because they are biological materials obtained from a crime scene or from the suspect that can provide definitive information regarding involvement in a crime. Analyzing DNA can lead to the identification of a suspect or victim, making it critical in forensic science.

In contrast, the other options involve forms of evidence that are not physical materials. Witnesses’ accounts represent testimonial evidence, which is based on individuals' observations and recollections. Audio recordings also do not constitute physical evidence in the strictest sense but are considered material evidence that captures sounds and voices, potentially related to an event. Prior convictions refer to a person's history of legal offenses and are considered character evidence rather than physical evidence. This highlights the distinctive role physical evidence plays in the investigative process, making DNA samples a quintessential example.