To Catch a Crook: The Spectrophotometer in the Crime Lab Reply

If you’ve ever seen an episode of “Law and Order” or “CSI,” then you likely possess a basic understanding about how forensic science plays a role in helping solve a crime. From fingerprints to mud stuck in tire treads, evidence of all types can help investigators figure out what happened and who is responsible.

Would you believe that one of the tools used by forensic scientists to solve crimes is actually a tool commonly used by professional painters? It’s true: you may think that a spectrophotometer exists simply to help match colors at the paint store or confirm color at a paint manufacturing facility, but in reality, spectrophotometers have a wide range of uses, including in the crime lab as forensic scientists work to understand what happened in a criminal event.

BYK spectrophotometer

A desktop spectrophotometer system.
Image courtesy of BYK

Spectrophotometers, like this one manufactured by BYK perform their evaluations of paint color by measuring the amount of light a sample absorbs and the amount it reflects. This tool includes two primary parts: the spectrometer for producing the light waves to be measured, and the photometer for measuring the intensity of the light once it has passed through the solution or substance. In professional painting, spectrophotometers measure the translucence of paint colors across the color spectrum to help determine the exact color composition of that sample. This information is relayed back to the paint mixer, for example, which allows the previously measured color to be replicated at the store.

In forensic science, the spectrophotometer is used to determine the color signatures of substances like carpet fibers. For example, let’s suppose a home was burglarized over Christmas. Investigators notice that the house has a unique color of carpet by the entry way the thief is presumed to have used. Later, a suspect is identified and a unique color of carpet fiber that might match the carpet from the house is located in the floorboards of the suspect’s vehicle. Forensic scientists could use a spectrophotometer to measure the color signature of each fiber and declare a match with reasonable certainty if the measurements were equivalent. Forensic scientists use color evaluation and measurement to compare and contrast not only carpet fibers, but also discarded paint flecks, chemicals, and other liquids that are material to an investigation.

Spectrophotometer in use

Diagram of use for a spectrophotometer.
Image courtesy of Virginia Tech University

Many other industries have practical uses for spectrophotometers as well. Companies that bottle liquids like olive oil or beer can use spectrophotometers to test color consistency after the product has been bottled, but before it has shipped out to the customer. Pharmaceutical companies can use spectrophotometers to confirm that medicines have the exact right dosages of each included chemical. Once you open your mind to all the places that quantifiable color measurement might be useful, the importance of a spectrophotometer in a variety of industries and institutions becomes crystal clear.



Click here to learn more about color measurement and the other practical uses of  tools like spectrophotometers outside of professional painting!

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