Which of the following is NOT a type of physical evidence?

In the context of crime scene investigation, physical evidence refers to tangible items that can be collected and analyzed to help reconstruct events or identify individuals involved in a criminal act. Hair samples, blood stains, and fingerprints are all examples of physical evidence because they are direct, physical items that can be gathered at the crime scene, preserved, and subjected to forensic analysis.

On the other hand, testimonies from witnesses are considered testimonial or circumstantial evidence rather than physical evidence. This type of evidence relies on the accounts and observations of individuals who witnessed or have knowledge about an event. While witness testimony can be crucial in establishing facts and providing context to a case, it does not involve a physical item that can be analyzed scientifically. Thus, it does not fit the definition of physical evidence, making it the correct choice for this question.