Latent bloodstain
Definition
A bloodstain that is no longer visible to the naked eye under normal lighting conditions, either because it has been diluted, cleaned, dried and faded, or deposited on a dark substrate. Luminol and fluorescein both target latent stains.
Related terms
- Barrier filter
- An optical long-pass filter placed over the camera lens and worn as goggles by the examiner during ALS examination; blocks the excitation...
- Chemiluminescence
- Light emission produced directly by a chemical reaction, without requiring an external light source. Luminol's reaction with haemoglobin in alkaline peroxide is...
- Excitation light
- The external light source used to excite a fluorescent molecule. For fluorescein the optimum excitation is around 490-510 nm (blue-green). The light...
- Fluorescence
- Light emission following absorption of light at a shorter (higher-energy) wavelength. Fluorescein absorbs blue-green excitation light and emits yellow-green light. The emitted...
- Haem iron
- The iron atom at the centre of the porphyrin ring in haemoglobin. It catalyses the luminol reaction by cycling between oxidation states...
Explained in
- Luminol and FluoresceinA bloodstain that is no longer visible to the naked eye under normal lighting conditions, either because it has been diluted, cleaned, dried and faded, or depo...