Blank control
Definition
A sample known to contain none of the target material, processed in parallel with real exhibits to detect laboratory contamination. A positive result on a blank indicates the process itself is introducing the target.
- Purpose
- Detects laboratory contamination during analysis
- Content
- Unused, clean material known to contain none of the target substance
- Processing
- Processed in parallel with case exhibits using identical methods
Common questions
What is a blank control used for?+
A blank control detects contamination introduced during laboratory analysis. It's an unused, clean sample that goes through the exact same collection and processing steps as the actual case sample. If the blank tests positive for the target material, the laboratory process itself is contaminating the samples.
How does a blank control work in practice?+
The blank control contains none of the target material and is processed in parallel with real exhibits under identical conditions. Since it shouldn't contain anything you're looking for, any positive result is a red flag that the lab workflow has a contamination problem.
Why are blank controls important in forensic analysis?+
They reveal whether contamination is coming from the evidence itself or from the laboratory. Without blank controls, you can't tell if a positive test result is genuine or an artifact of poor lab technique.
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Explained in these topics
- Botanical Evidence Collection and PreservationAn unused, clean sample processed through the same collection and laboratory workflow as the case sample, used to detect any contamination introduced during an...
- Quality Assurance, Reference Collections, and AccreditationA sample known to contain none of the target material, processed in parallel with real exhibits to detect laboratory contamination. A positive result on a blan...