Forensic Lighting - ALS

Crime & Forensics;

​

Forensic Inspection Lighting helps you see what your eyes can’t see at a crime scene.  At a crime scene, fast and accurate detection of possible traces is of vital importance with many biological fluids being fluorescent in nature.

 When such traces are illuminated with light at 365nm they fluoresce and are detectable to the investigator. The degree to which various substances become visible to the eye when using different filters depends on the state of the substance and the surface on which the substance exists.

 

 Deciding what light source to use to achieve the best result in finding traces at the crime scene is an art. It takes years of experience to learn what light to use depending on the occasion - it’s not an exact science.

 New users using ALS (Alternative Light Sources) can of course use combinations of light and goggles to determine the best option for that occasion using trial and error until confidence and knowledge has been built up.  We make it possible for each user to put together their own unique ALS kit.

 

No crime scene looks the same & no crime scene investigator uses the same method! 

​

Detecting Blood Stains;

​

There are several common ways to detect blood at the crime scene.

 One very easy and quick way to detect blood is to use UV light.

 When to use UV light to detect blood:

•  Reduce the risk of collecting unnecessary stains by knowing which areas to investigate through the use of UV.

•  Detect blood on dark, red or violet surfaces.

•  Find blood stains that are concealed by paint.

 

Reduce the risk of collecting unnecessary stains;

​

By using ultraviolet light it is possible to do an effective and quick check for possible bloodstains. A bloodstain exposed to UV light absorbs all light of that bandwidth and will not reflect back – that is to say, it does not fluoresce in any way. Thus the stain will appear black under UV light which is often a misconception held by many.

  Although not a conclusive test for blood, it is an effective presumptive test and can often eliminate the unnecessary collection of stains that appear to be blood that are actually from another source.

 

Dark surfaces;-

 

The UV light source is also effective for providing sufficient contrast of bloodstains that are found on red- or violet-coloured objects. Such stains often fade into the background so well that it is impossible to photograph them. Ultraviolet light often provides sufficient contrast between the background and stain to allow the stains to be visualized in a photograph. Blood concealed by paint It is not uncommon that a perpetrator of a crime tries to get rid of potentially incriminating evidence. This may include painting over areas that have been exposed to blood. To the naked human eye it is next to impossible to see that a blood stain has been painted over. By using ultraviolet light however, it is possible to detect blood stains that have been concealed by paint