Substrate Control
Definition
A sample of the unstained surface material from an area adjacent to a body fluid stain, collected alongside the stain and processed through the same analytical workflow. The substrate control distinguishes background DNA or chemicals in the surface material from evidence contributed by the biological stain.
Related terms
- Touch DNA
- Minute quantities of epithelial cells transferred by skin contact with a surface, without leaving a visible stain. Collected by swabbing contact points...
- Alternate Light Source (ALS)
- A device emitting light at selected wavelengths (typically 415 to 535 nm) used to detect biological fluids that fluoresce or absorb light...
- Azoospermia
- The absence of spermatozoa from ejaculated semen, resulting from obstructive causes (vasectomy, ductal blockage) or non-obstructive causes (testicular failure). Azoospermic semen contains...
- Chain of Custody
- The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes...
- Cross-Checking
- The practice of running two different presumptive tests on adjacent cuttings from the same stain. Concordant results (both positive or both negative)...
- Differential Extraction
- A two-step DNA extraction procedure used when a stain contains both sperm cells and non-sperm epithelial cells. The first step lyses epithelial...
- Double-Swab Technique
- A collection method for dried biological stains in which a moistened swab rehydrates and lifts the stain from the surface, followed immediately...
- Leucomalachite Green (LMG)
- The reduced, colourless form of malachite green. It is oxidised to the coloured malachite green form by active oxygen released when haemoglobin...
- Malachite Green
- A synthetic triphenylmethane dye with an intense blue-green colour in its oxidised form. It is a common industrial dye and the coloured...
- Presumptive Colour Test
- Any rapid field or laboratory test that produces a colour change in the presence of a target substance. Positive results are indicative,...
- Prostate-Specific Antigen (PSA)
- A serine protease glycoprotein (also called p30) secreted in high concentrations by the prostate gland into seminal plasma. The primary immunological marker...
- Reference Sample
- A biological sample collected from a known individual (victim, suspect, or elimination source) for comparison against scene stains. Typically a buccal swab...
Explained in these topics
- Biological Evidence Collection ProtocolsA sample of the surface material on which a stain was deposited, collected from an unstained area adjacent to the stain. Used by the laboratory to detect backg...
- Leucomalachite Green TestA test of the same material (fabric, surface, soil) at an area that shows no visible staining. A positive substrate control indicates the material itself conta...
- Semen, Saliva and Other Body Fluids as EvidenceA sample of the unstained surface material from an area adjacent to a body fluid stain, collected alongside the stain and processed through the same analytical...