Selection of Samples for Testing
Care should be taken in selecting a single sample (or at least the minimum number of samples) for testing that will give meaningful/useful results for a particular case. There is no point in testing samples in category 5 cases. (See Determining Which Samples to Test). Criteria for selection of the sample may include:
- Which sample would prove innocence if the defendant is excluded as a donor.
- Which sample is of sufficient size and quality to likely give reliable and interpretable test results.
- Which sample is of sufficient size to permit repeat or additional testing at a later time.
- Which probative sample has been collected, preserved, and handled appropriately to ensure the integrity of the sample results.
- Which sample has sufficient chain-of-custody documentation.
- Are additional samples available that have not been evaluated previously? (See discussion in chapter 3 on reasons for inconclusive results.)
The availability of and necessity for samples from known individuals who should be tested for exclusionary purposes will need to be carefully considered. For example, in sexual assault cases where the defendant is excluded as a donor of the DNA, it is imperative that a sample from the victim and any known consensual partner(s) be tested in order for that exclusionary result to provide exculpatory evidence. Additionally, testing of the victim's sample in sexual assault cases can serve as a built-in control to confirm that the testing has been performed correctly and that the questioned sample is, in fact, linked to that victim.
Go to the Next Section: Retention of Samples for Future Testing
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