124 Forensic dentistryCombinations of these references may also be extremely helpful, and the
laboratory managing the case should be consulted. Recall, too, that earlier in
the chapter, paternal lineage markers (Y-STRs) and maternal lineage markers
(mtDNA), while not unique to the individual, may still provide inclusion-
ary or exclusionary results. In combination with circumstantial and other
forensic evidence, the results can be statistically compelling. The lineage
markers also offer the potential for a reference source that spans many gener-
ations. For example, a great-grand-nephew may serve as a mtDNA reference
for a victim that is missing decades earlier.
There are many commercial buccal swab collection kits on the market
today.59–62 The simplicity and painlessness of the procedure combined with
the minimal training requirement for the person performing the collection
has launched this method of DNA reference collection to the forefront of use.
The other advantages that buccal swabs offer over blood-based collection tech-
niques are the ease of self-collection and greater tolerance of this procedure in
children and uncooperative donors. Although the commercial market offers
a series of ingenious collection devices, suitable results can be obtained with
sterile cotton-tipped applicators found in most medical supply stores.
Most buccal swab collection protocols are essentially the same. Start by
documenting the identity of the donor or establish a unique sample number
if the identity of the donor is unknown.
Wear gloves and avoid contaminating the swabs by contact with any sur-
face or aerosol other than that of the donor:
- Have the donor thoroughly rinse his or her mouth with water and
expectorate. Repeat. - Wipe one side of the buccal mucosa with 2 × 2 sterile gauze.
- Firmly stroke the dried area of the mucosa ten times with the swab,
slowly rotating the cotton tip each time. Avoid the site near the open-
ing of Stenson’s duct if possible. - Repeat the process with a second swab on the contralateral cheek.
- Allow both swabs to air dry in a contamination-free environment for
at least thirty minutes. - Place in a prelabeled paper envelope or wrapper and seal with evi-
dence tape. - Verify that the unique labeling and correct contents of the packet are
documented; initial and date the seal for continuity purposes. - Complete the chain-of-custody form and ship to the laboratory as
directed, maintaining a cool, dry, ultraviolet-light-free environment
wherever possible.
Rinsing prior to DNA collection reduces the presence of food par-
ticles or debris, such as chewing tobacco, and even reduces the possibility