Collection and Preservation of Low-Template DNA Evidence
The entire item can be collected and submitted to the laboratory or the item can be sampled prior to submission to the laboratory. Either way, collecting a sample for low-template DNA testing is not difficult. It is, however, the singlemost important determinant in successfully getting a DNA profile.
To preserve a sample, package the item in a clean bag. Contamination must be avoided.
When collecting a sample, the thing to look for is C.R.U.D. (our mnemonic device for “cellular residue and unknown debris”). It is the grayish stuff found on your necklace, ring, or the back of your watch or bracelet. To collect it, a variety of tools can be employed:
1. Swabs – Good for smooth surfaces or surfaces with ridges.
2. Toothpicks – Good for nooks, crannies, and ridges.
3. Tapelift – Good for smooth surfaces, nooks, crannies, and ridges.
4. Vacuum-swab – Good for fabric.
Collecting a better sample produces far better results than collecting a bigger sample. For example, swabbing an entire baseball bat with one swab is worse than swabbing the grip for the assailant and swabbing other end of the bat for the victim. This does two things: 1) it avoids artificially creating a mixture and 2) it gives a more concentrated sample from each area, thus increasing the odds of getting good results.
Preservation of low-template DNA items/samples is quite simple. Larger items should be packaged in paper since the paper can breathe and allow any moisture trapped inside to escape. (If the samples are collected using a vacuum technique, small pieces of tape, or a toothpick, then the samples can be placed in a small plastic/glass tube to avoid loss.) Cool, dry and undisturbed are the other requirements. Cool can be a normal room temperature, not excessively hot or cold. Dry is just that - dry. Not to the extent of a desert, but not excessively moist either. Undisturbed means that movement of the item will not cause excessive contact with the packaging. For example, a baseball bat would be better packaged in a gun box than a paper bag. In a paper bag the bag would rub against the bat every time the bat was moved. Cells could be jarred from the bat and become loose in the bag only to be lost when the bag is opened. In the box, the bat could be secured so there is less likelihood of cells being jarred loose.
To preserve a sample, package the item in a clean bag. Contamination must be avoided.
When collecting a sample, the thing to look for is C.R.U.D. (our mnemonic device for “cellular residue and unknown debris”). It is the grayish stuff found on your necklace, ring, or the back of your watch or bracelet. To collect it, a variety of tools can be employed:
1. Swabs – Good for smooth surfaces or surfaces with ridges.
2. Toothpicks – Good for nooks, crannies, and ridges.
3. Tapelift – Good for smooth surfaces, nooks, crannies, and ridges.
4. Vacuum-swab – Good for fabric.
Collecting a better sample produces far better results than collecting a bigger sample. For example, swabbing an entire baseball bat with one swab is worse than swabbing the grip for the assailant and swabbing other end of the bat for the victim. This does two things: 1) it avoids artificially creating a mixture and 2) it gives a more concentrated sample from each area, thus increasing the odds of getting good results.
Preservation of low-template DNA items/samples is quite simple. Larger items should be packaged in paper since the paper can breathe and allow any moisture trapped inside to escape. (If the samples are collected using a vacuum technique, small pieces of tape, or a toothpick, then the samples can be placed in a small plastic/glass tube to avoid loss.) Cool, dry and undisturbed are the other requirements. Cool can be a normal room temperature, not excessively hot or cold. Dry is just that - dry. Not to the extent of a desert, but not excessively moist either. Undisturbed means that movement of the item will not cause excessive contact with the packaging. For example, a baseball bat would be better packaged in a gun box than a paper bag. In a paper bag the bag would rub against the bat every time the bat was moved. Cells could be jarred from the bat and become loose in the bag only to be lost when the bag is opened. In the box, the bat could be secured so there is less likelihood of cells being jarred loose.
