Split-Sample Protocol
Definition
The practice of dividing a forensic extract into two portions before analysis, one for prosecution analysis and one archived for potential defence re-testing. Required by CPIA 1996 (UK), Brady disclosure obligations (US), and ENFSI guidelines (EU) to preserve the defence's right to independent testing.
- Purpose
- Preserve the defence's right to independent retesting
- UK basis
- CPIA 1996
- US basis
- Brady disclosure obligations
- EU basis
- ENFSI guidelines
- Typical split
- One portion for prosecution analysis, one archived
Common questions
What happens if a sample is too small to split?+
When the extract volume is insufficient for a true split, the analyst documents the shortfall and, where possible, retains a portion of the original unextracted material instead, so the defence still has something independent to test.
Does the split-sample protocol apply to DNA as well as chemical extracts?+
Yes, though DNA cases usually satisfy it by retaining an untested reference or crime-scene stain rather than splitting an extract, since PCR-based methods can consume very little material.
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