What method is used to collect questioned stains from non-absorptive surfaces?

The collection of questioned stains from non-absorptive surfaces requires careful handling to ensure that the sample is not contaminated and is preserved for analysis. Using a sterile swab dampened with sterile water is the appropriate method for this situation.

This technique allows for the gentle lifting of the stain without damaging the surface or altering the chemical composition of the sample. The sterile swab ensures that no external contaminants are introduced, and the dampness helps to dislodge the stain more effectively compared to a dry swab. Once the stain is collected, it can be properly packaged for forensic analysis.

In contrast, using a plain cloth may not provide the precision needed for delicate samples and could introduce fibers or other contaminants. A vacuum might seem useful in some contexts, but it could disrupt the stain or not allow for proper collection. Using a hair sample is irrelevant in this context, as it is not a method for collecting stains but rather a separate type of evidence.