Introduction
A Forensic Light Source (FLS) is a powerful tool used in forensic science that emits ultra-violet, visible, and infrared components of light. It is a versatile device that filters the light into individual color bands, which enhances the visualization of evidence by various light interaction techniques like fluorescence, absorption, and oblique lighting.
The FLA is a crucial tool in forensic investigations, as it can be used to detect various types of evidence, such as bodily fluids, fibers, and latent fingerprints. FLS detects latent fingerprints on surfaces like paper, metal, plastic, and glass. The device helps investigators to visualize and enhance the fingerprints by providing illumination in the UV region.
Moreover, FLS has many applications in different fields, such as art authentication, document examination, and counterfeit detection. In art authentication, FLS can detect the presence of various materials, such as varnish and paint, which helps to determine the artwork’s authenticity. In document examination, FLS can detect alterations, erasures, and ink differentiation in documents. In counterfeit detection, FLS can help to detect counterfeit currency and credit cards by revealing hidden security features.
Latent Fingerprint Detection
Forensic Light Sources enhance the detection of latent fingerprints by complementing traditional light sources with fluorescent processes, expanding the range of surfaces from which fingerprints can be detected. This means that fingerprint evidence on complex surfaces such as thin plastic bags, rigid duct tape, thin aluminum foil, heavily grained wood, concrete walls, bricks, printed glossy magazine pages, paper products, and others may go undetected or even dismissed using traditional methods. As a result, Forensic Light Source techniques have been developed and successfully utilized for revealing latent prints on these and many other types of textured, background-masked, fragile, and contaminated surfaces.
However, it is essential to note that different wavelengths are required for processing different types of surfaces, making a Forensic Light Source with tunable or multiple wavelengths a coveted tool for any crime scene investigator. This tool can be handy in situations where traditional methods may not suffice, such as in complex crime scenes with various surfaces and materials.
Body fluids
Body fluids such as semen, saliva, and vaginal fluids naturally fluoresce, emitting light when excited by specific wavelengths of light. Therefore, a light source can be used to locate these fluids, which can be a valuable tool for a crime scene investigator. This technique allows the investigator to narrow down specific locations of stains for collection instead of testing entire large pieces of evidence, such as mattresses, carpets, sheets, and clothing. Additionally, this technique can help investigators detect dried body fluids, which can be challenging to see with the naked eye.
It’s worth noting that while body fluids will fluoresce under a standard UV black light, many objects, such as clothing and sheets that may contain them, will also glow, making it difficult to detect evidence. To overcome this issue, it is necessary to tune to longer wavelengths to eliminate background interference (background rejection). This technique, known as background rejection, can help investigators to isolate the fluorescence of body fluids from other sources of fluorescence, allowing for more accurate detection and analysis of evidence.
Hair and Fibers
Using two illumination methods, Forensic Light Sources can be used to locate hair and fibers. The first involves oblique or parallel lighting of a surface, such as a floor or a carpet, with a strong white light, which will reveal small particles like hair and fibers for collection. The second method involves UV or blue light to make some hair and fibers glow and stand out for collection. This method is highly effective in locating otherwise difficult evidence to see with the naked eye. By combining both approaches, investigators can identify and collect a wide range of evidence to help solve the case.
Bruises/Bite Marks/Pattern Wounds
Forensic light sources are instrumental in the investigation of physical injuries. By illuminating bruises and patterned wounds with specific wavelengths of light, a wealth of invisible information can be revealed under normal white light illumination. For example, the pattern of a bruise on a suspect’s palm can reveal the weapon used, while details of a bruise on a victim, such as a bite mark or shoe mark, can link a suspect to the victim.
However, it’s important to note that using multiple wavelengths is necessary to investigate a physical injury thoroughly. This is because different colors penetrate the skin to different depths. Therefore, depending on the depth of the bruise or wound, the instrument’s wavelength may need to be adjusted. For instance, deep wounds may require infrared illumination for sufficient skin penetration.
Questioned Documents
Inks are a complex mixture of chemicals that can have different formulations, even within the same apparent visible color type. The properties of the ink can vary depending on the manufacturer, the age of the ink, and the storage conditions. A tunable Forensic Light Source is an advanced tool that can identify slight variations in ink type by viewing ink responses as the color of the light is tuned through the visible and infrared regions. This examination would reveal that two different pens were used on the document, regardless of the forger’s skill. This is because the different ink formulations would respond differently to the different wavelengths of light.
Typically, evidence is visualized in the infrared (IR) region, which is not visible to the human eye. This requires specialized equipment such as IR-sensitive film or a digital/video camera with IR sensitivity. Such equipment allows forensic examiners to detect and analyze the ink on a microscopic level, revealing hidden details that are not visible to the naked eye. This is particularly useful in cases where a forger has attempted to alter a document by erasing or writing over existing text. By analyzing the ink used in these alterations, forensic examiners can determine the order in which the text was written or modified, providing valuable information for criminal investigations and court cases.
Gun Shot Residues/Explosive Residues
Several types of residues can be found in ammunition and explosives that can fluoresce, making them visible using a tunable Forensic Light Source. This can be a valuable tool in detecting the presence of such residues without touching the surface of the item being examined physically.
In addition, it is possible to identify the shooter and the location from which the shot was fired by examining the clothing of any witnesses or observers present at the scene. This is due to the presence of ejecta residue that is expelled from the gun barrel when it is fired. The same residue would also be present on the shooter’s hands, which can be a potential link between the shooter and the weapon used in the crime.
It is important to note that while this approach can be highly effective in certain circumstances, it is not a foolproof method of identifying the shooter or the location of the shot. Other factors, such as weather conditions, the distance between the shooter and the target, and the type of ammunition used, can all impact the results of this type of analysis. Nonetheless, it remains a valuable tool in the field of forensic investigation and can often provide crucial information in the course of a criminal investigation.
Human Bone Fragments, Tire Tracks, Shoe Prints, Drugs, etc.
Forensic Light Sources can be used to detect various items, including human bone fragments, tire tracks, shoe prints, and drugs. The specific wavelengths required for detection will depend on the investigated substance and the surface on which it is found. However, with the right combination of wavelengths and illumination techniques, forensic investigators can reveal a wealth of information that would be invisible under normal white light illumination.
Conclusion
Forensic Light Sources can be used for many different applications. Those listed here are only a few compounds that will fluoresce in the environment. Users are encouraged to experiment, trying different wavelengths on different surfaces. You may be surprised by what you find.
In conclusion, FLS is a crucial forensic science tool that helps investigators detect various types of evidence. In addition, its versatile nature and a broad range of applications make it a valuable tool in different fields.
