By Dr. Peter Bilous, Eastern Washington University
We have all seen the “CSI” dramas on television – with crime fighting “super heroes” dashing from the streets to the labs, using numerous gadgets along the way, to solve crime. However, in reality, forensic scientists are not routinely required to attend crime scenes. Instead, they are hard at work in the lab, applying the latest technologies and chemistry principals to evaluate evidence from the crime scene.
Forensic scientists are called upon to answer the “who, what, when and where” of crimes. Their training enables them to identify unknown substances such as drugs; link unsolved crimes together through DNA and fingerprint databases; establish associations between victims and suspects (through hair, fiber, fingerprint or DNA evidence); and provide investigative leads (linking types of weapons that fire particular bullets or types of vehicles that leave paint chip evidence at hit-and-run scenes).
Here are some of the processes and technologies used to answer these questions.
Forensic scientists utilize a set of chemical and biochemical tests, as well as various light-based instruments, to locate physical evidence. Portable high-intensity light sources that are used by crime scene investigators to locate fingerprints are also used by forensic scientists in the laboratory to find forensic evidence such as carpet fibers or body fluid stains. Once located, evidence is classified by group or class of compounds and/or identified by chemical nature to determine the types of screening and identification tests that will be used.
Depending on the nature of the crime being investigated, forensic scientists may need to look for chemical evidence – drugs, poisons, paint chips, fibers and explosive residues. Chemical-based screening tests and/or microscopic examinations are used to classify materials. Physical properties such as surface features, colors, melting points and various optical properties can be helpful in classifying fibers, drugs, paint chips or soil samples.
Micro-spectrophotometers are used to determine light absorption properties of trace quantities of physical evidence. Identification may require the use of chromatography to separate the components of a mixture followed by instrumental methods of analysis such as FTIR-spectrophotometry or mass spectrometry to determine the chemical composition of evidence. Raman spectroscopy, based on the light scattering properties of the sample being examined, is particularly useful for identifying pigments, dyes, fibers, drugs and minerals.
Perpetrators of crimes may leave behind biological evidence, including blood, semen, saliva or skin cells. Various color-based chemical screening tests are employed to tentatively identify biological material. Identification tests include microcrystal tests (e.g., the Takayama microcrystal test for blood) or immuno-chromatographic tests that detect the presence of hemoglobin, a component of red blood cells.
Forensic DNA typing analysis – involving the amplification (copying) of a set of genetic markers that exist in many forms within the human population – are then conducted on the biological materials to determine the donor source. The polymorphic nature of these markers provides a means to discriminate between individuals.
With the increased application of science and technology to solve crime – and all of that television promotion – it’s no surprise that forensic science is growing in career popularity.
Eastern Washington University’s forensics program, started in 2003, is popular with students. EWU is fortunate to have a Washington State Patrol Regional Crime Lab located right on campus. This, in addition to other on-campus labs, gives students a unique opportunity to interact with seasoned professionals, research actual cases and solve mock crimes.
After a recent community presentation, I had a junior high school student approach me to ask detailed questions about forensic science. It reminded me that all of those television dramas aren’t so bad after all if they are attracting youth to new technologies that work hand-in-hand with good old chemistry principals – all for a very good social cause.
Peter Bilous, PhD, is an Associate Professor in the Department of Chemistry and Biochemistry at Eastern Washington University.