What is a common method for collecting DNA evidence at a crime scene?

Using sterile swabs or clothing is a common method for collecting DNA evidence at a crime scene because these materials are designed to minimize contamination and ensure the preservation of the biological evidence. Sterile swabs are specifically manufactured to collect samples without introducing foreign DNA or other contaminants that could compromise the integrity of the evidence. They are used to gently rub surfaces or directly collect substances like blood, saliva, or skin cells.

Additionally, clothing that is clean and uncontaminated can also be used to gather samples in a way that preserves the original state of the DNA for analysis. This careful approach is crucial in forensic investigations, as it helps to ensure that the collected DNA can be reliably analyzed and matched to potential suspects.

Other methods, such as using regular cloth, can introduce contaminants that might interfere with DNA analysis, while metal tools may scratch or damage evidence, leading to degradation. Conducting interviews with suspects, although important in investigations, does not directly involve the collection of physical DNA evidence, making it irrelevant in this context. Therefore, the use of sterile swabs or appropriate clothing stands out as the best practice for collecting DNA evidence effectively.