which led light Finding Forensic Evidence Using Lights

by:Leimove     2020-03-07






















































































Let\'s face it.We 've all seen CSI, Bones and many other forensic TV shows where investigators can find evidence anytime, anywhere.The reality is that it (unfortunately) is not as easy as TV.This lens exists to help people understand how to use forensic flashlights and headlamps, also known as forensic light sources (FLS) or alternative light sources (ALS ).I promise to keep things as simple as possible here for you.I'm not going to discuss lasers here because they can be very expensive and not usually portable.Forensics is a science, and we need the right tools and conditions to visualize evidence.There are 3 absolutely required.Fluorescent dyes or powders, such as Luminol, help a lot.When looking for fingerprintsVery simple....The darker we are, the more evidence we can see.Ambient lighting is a fancy name for room background lighting that reduces the amount of fluorescence or absorption we see.If there is too much light in the environment, it is easy to miss the evidence.There is a lot of debate about the best wavelength to use.The reasons include the difference in global air density, the difference in the way people train, and the personal preferences of users.The evidence in the dry Arizona air will remain different from the evidence in the more humid Southeast.In addition, a person's race and the background on which the evidence is based will also help to select different wavelengths in different situations.For example, 450 nm (blue light) may be good to help you find blood in Scene A, while 470 nm may be better to find blood in Scene B.We choose the appropriate wavelength based on the evidence sought.The wavelength is represented by nanometers (nm), and each color has a series of wavelengths.The range I Included below is arbitrary.I limit the color below to the most commonly used color in forensics.There are two commonly used blue light and ultraviolet light.Used to detect bruises, serum evidence (semen, saliva, urine), general crime scene searches (hair, fibers, etc ).Used for finding blood stains, GSR (gun residue), general crime scene searches (hair, fibers, etc ).IR light (770 to 2,500 nm;AKA near-The filter blocked the light that was not absorbed by the evidence.The forensic filter can be a camera lens, goggles, or plastic sheet in a specific tone.The filters we use depend on the evidence we are looking for and the wavelength we are using.Use color filters if you have a camera.If you are an investigator without a camera, use color goggles.Red, orange, yellow and transparent filters are used for forensics.Orange and red are the most useful.The yellow and orange filters are used with blue, UV, green and green light.Use the red filter only when the green light is available.Transparent can only be used under UV light.IR lights are a bit tricky.No filters or goggles will produce results.To visualize any evidence, a forensic camera with infrared function is required.Camera manufacturers such as Fuji (IS Pro) and Nikon (D90) have made such models.The price of medical light sources varies greatly....The pen light can be as low as $10 and high-The price of a terminal laser could be as high as $30,000.Some of the newer LED light sources on the market represent the best value and maximum cost between $20 to $800 per wavelength.The greater the power of light, the farther you are from the evidence.You need to be very close (within 1 feet) to see it with a weak light source.When looking at small controlled areas like a computer keyboard, these functions can still work well.A very powerful light source allows you to be 30 feet away from the evidence and still see it.These are best used in larger, uncontrolled scenarios.Some manufacturers, such as FoxFury, list the operating distances (rods) they recommend ).Your purchase decision is based on how much light is needed.This issue is rarely looked at, but it is important to note.What we are talking about here is the accuracy of the wavelength.The scientific name for this is spectral brightness.The precise wavelength of the light source is emphasized, but the specificity of the wavelength is often ignored.A more precise wavelength means that more of the required colored light will point to evidence, which translates to better observed fluorescence/absorption (and less wasted light ).Some old halogen lamps have wavelength specificity of plus or minus 50 nm.Therefore, a 470 nm light with this specificity will emit everything from 420 nm (in the UV spectrum) to 520 nm (in the green spectrum.Like The Bell Curve, most of the light is still blue (between 450 and 490 nm), but quite a bit (about 20%) so the light will not and will not be in the non-usable range.The updated LED light source is more accurate, and some even have the specificity of plus or minus 3 nm.The same 470 nm goes off between 467 and 473 nm, the only blue.Therefore, more light will be absorbed, which will make it easier for us to see the evidence and take pictures.Here is a Coca-Coke can be processed with fluorescent dyes.Use a 525 nm (green) light source.This photo was taken with a camera with an orange filter on the lens.The fingerprint is easy to spot because it is dark and uses the correct wavelength/filter pair.This is the fingerprint (potential fingerprint) on the 9mm pistol magazine ).Like the picture above, use a fluorescent dye and take the image using a camera with an orange filter on the lens.It is also possible to use medical sources to locate drugs.Different drugs emit different fluorescence/absorption.If you hit marijuana with blue light (assuming it's dark, you're using an orange filter), it will appear in red-The human eye is brown and the camera is pink.There are some false positives, so this type of investigation is only a presumed search, not a definite one.Hands-Free vs.Hand-Everyone has their own benefits but will finish the work.Hands-These include headlights and utility lights that can be caught on investigators.Two free hands for multiple peopleAssignment of tasks (taking notes, lifting weights, etc ).Hand-In forensics, the use of flashlights is much more common.Possible cross-Forensic lights are available on almost every episode of forensic TV shows, such as CSI and Bones.Sometimes large lights are displayed in the lab, while small lights are displayed on site and in the lab.Blue light usually shows better on TV compared to UV light.FoxFury hammer head 470 nm (blue light) ALS flashlight above is a scene in the popular TV show bone.More forensic evidence is usually found without a light source.Light sources can help locate smaller evidence, including biological fluids, hair, fibers, etc.Hard to see with the naked eye.If properly operated, the light emitted from the correct light source can be seen through the filter (lens, goggles.This section provides a brief overview of the light physics involved.The light emitted from the light source is either absorbed by evidence or scattered (reflected back to the user, etc ).).The filter (lens, goggles) blocks the scattered light and only allows us to see the absorbed light (fluorescence )...As long as we use the correct wavelength and lens for a given type of evidence.Actually, let's say, we look for hair with a UV light source of 395 nm.Our goal is where we think the evidence may exist.The ultraviolet light emits a purple/purple light.The hair absorbs some UV rays and reabsorbs them.Emitted at a longer wavelength (above 395 nm ).In this case, when the hair is seen through the orange filter, the hair appears green or yellow.Green (~ 520 nm) and yellow (~ Wavelength ratio of 570 nm to ultraviolet (~ 395 nm) long.The filter blocks UV rays and makes the evidence stand out.Using a no (or incorrect) filter causes a large amount of reverse scattering to be seen, which will make it difficult to see the evidence.FoxFury's ALS utilizes LEDs and is available at a specific wavelength.In some cases, we may provide two models of different wavelengths for a light color.We selected these wavelengths after extensive testing using different evidence in various dilution.We also provide white light.UV -Blue -Cyan -Green -IR -
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