What is the function of a swab in evidence collection?

The function of a swab in evidence collection is primarily to collect biological samples such as blood or saliva. Swabs are designed to absorb and retain these types of fluids, which are crucial for forensic analysis. For instance, they can be used to gather DNA evidence, which can provide vital information in identifying a suspect or victim in a crime scene investigation. This method allows for the careful and sterile collection of biological material, ensuring that the evidence remains uncontaminated for subsequent analysis in a laboratory setting.

Other options, while relevant to the broader context of crime scene investigation, do not directly pertain to the specific application of swabs. Using swabs for tasks other than collecting biological samples would not utilize their intended purpose effectively.