Double-Swab Technique
Definition
A collection method for dried biological stains in which a moistened swab rehydrates and lifts the stain from the surface, followed immediately by a dry swab that absorbs the released material. Both swabs are submitted together. Validated to recover more cellular material than a single swab on porous substrates.
- DNA yield improvement
- Recovers more cellular material than single dry swabbing
- First swab condition
- Moistened with sterile water
- Primary applications
- Bite marks, licking cases, dried saliva on skin and porous surfaces
Common questions
Why use two swabs instead of just one?+
The first wet swab rehydrates dried biological material like saliva and loosens cells stuck to the skin or wound. The second dry swab then lifts that material away, recovering more cellular debris than a single dry swab alone could achieve.
What is the double-swab technique used for?+
It is a DNA collection method developed for bite marks, licking injuries, and other cases where saliva residue is thin or dried. It works on skin wounds, porous substrates, and anywhere you need to recover both cells and proteins from dried secretions.
What liquid is used to wet the first swab?+
Sterile water is the standard wetting agent. It rehydrates the dried deposit and resuspends the biological material so the second dry swab can absorb it more effectively.
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