There’s a breakthrough underway in law enforcement that can have a deep impact on crime-solving efforts.
Cutting edge spectroscopy applications are beginning to make inroads into crime scene substance identification. Researchers are exploring how these complex spectroscopy methods can be used in law enforcement activities.
Biological stains are one area crime fighters focus on. These can be used to identify persons of interest.
Biological stains include blood, saliva, semen, vaginal fluid, sweat and urine. Body fluid traces are important because they are the main source of DNA evidence. Currently, police use various biochemical tests to detect and identify body fluids.
But those tests are destructive – they alter the sample. The tests are also presumptive, and generate many false positives.
Raman spectroscopy and ATR FTIR (Attenuated total reflectance Fourier-transform infrared spectroscopy) are vibrational technologies that are more sensitive and can more accurately identify body fluids.
Researchers are using Raman technology as the first method to develop a universal, confirmatory test of body fluids. Raman is also a non-destructive technique and does not affect the sample as it’s tested.
Raman is being used in research to develop a non-destructive fingerprint of the chemical makeup of a substance. Automated software is also being developed to identify all the main body fluid traces for samples on a noninterfering aluminum foil substrate.
One hitch is examining samples that are on common substrates like carpets, floors, tiles, or whatever you find at the crime scene. Software is under development to detect dry body fluids on these substrates, as to make identification without touching the biological sample.
The next challenge is to transfer this technology from a desktop instrument to a handheld instrument that travels to the crime scene. Like a portable, handheld Raman instrument, for example. Prototypes are being tested in the lab now. The challenge is to develop methodology and make it economical to law enforcement agencies.
The upfront costs of such an instrument would be mitigated by the less expensive use of consumables, as is used now in biochemical tests. The portable Raman spectrometer could also be used by law enforcement to identify illicit drugs.
One researcher is working on phenotype profiling and can determine the sex, race and age of the donor based on a biological stain. This helps investigators build a profile of the suspect, a critical step in solving crimes. The technique is not ready for field use yet.
Gunshot reside can also be examined using Raman spectroscopy to identify the caliber of the weapon used in a discharge. Investigators can also use Raman to match the residue found on a victim or perpetrator with a sample of the gunshot residue in a test.
Raman spectroscopy can detect and characterize organic and inorganic particles, helping to overcome the identification of lead-free ammunition, a new trend in our greener world. This ammunition typically defies traditional testing methods. Raman spectroscopy is looking for molecular composition. Raman picks up molecules’ chemical structures, overcoming the limitations of traditional testing methods.
The ultimate goal is to develop black box-type instruments that can go out in the field and make these substance identifications. That goal is between three and five years down the road.
The Federal Bureau of Investigation uses Energy Dispersive X-Ray Spectroscopy (EDS or EDX) technology, like that made by HORIBA, in its analytical arsenal. The FBI built a large library of duct tape data for crime scene analysis using the technology.
An EDS analyzer is suited for qualitative and quantitative foreign material and composition analysis. The technique detects X-rays emitted from the sample during bombardment by an electron beam to characterize the elemental composition of the analyzed volume.
Crime scene investigators use ultra-violet and infrared fluorescence techniques in conjunction with lasers for identifying fingerprints. They also use fluorescence for document analysis, mainly in characterizing inks, and to identify drugs, glass, petroleum products and biological samples.
Investigators even use fluorescence spectroscopy to identify saliva stains on various objects.
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