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Authentic tools make all the difference in forensic lessons.
Professional forensic work requires an understanding of the scientific and mathematical principles involved in the methods used. As such, forensic science lessons serve as an excellent opportunity for teachers to communicate STEM principles to students. Let’s look at a few examples from modern forensic and crime scene investigation work.
Consider the development of latent fingerprints using chemicals. There is a specific recommended sequence for the use of chemicals:
Iodine > 1,2 Indandione DFO > Ninhydrin > Silver Nitrate > Physical Developer
Failure to process in this order (using the proper methods in a controlled environment) and to understand other factors involved could result in the destruction of latent prints and loss of critical evidence. Teach this sequence to your students now—and they will benefit later in practice.
Other great topics to include in your forensic curriculum that are important but often overlooked include crime scene documentation, proper evidence marking and handling, maintaining chain of custody, and methods of forensic analysis. The proper documentation and capture of evidence is critical to helping determine what happened at a crime scene. If you train your students to follow protocols, they will have a base to work from when they learn an employer’s protocols (as outlined by a district attorney and department leadership).
Modern CSI and forensic work involves the application of scientific principles and techniques, some of which are almost 100 years old. Others have been developed more recently. The common thread among the techniques is the use of reliable, high-quality forensic products that professionals can trust.
There are advantages to using authentic forensic products in the classroom as well. For example, forensic techniques for fingerprinting and latent fingerprint development can be very tricky and also very messy. The inkpads used by law enforcement for fingerprinting have special ceramic bases designed to deliver just the right amount of ink for good ridge detail. We sometimes see stamp pads used for classroom fingerprinting exercises. The pads usually have felt bases that do not limit the amount of ink, resulting in poor prints and a mess.
CSI and forensic professionals understand and apply the science behind the tools of the trade to help solve criminal cases and advance justice. They count on the tools they use. They practice their techniques. Consider the implications if forensic tools are not used properly.
With latent fingerprint development, we sometimes see charcoal or other materials used to develop latent prints. These substances often adhere to everything, resulting in loss of fingerprint detail. Forensic fingerprint powder is micro-milled into small particles for maximum ridge definition and consists of components that are combined to adhere to the moisture, oils, and fatty deposits left behind in a latent fingerprint. Using the right type of powder on the recommended surface results in good ridge detail, better definition against backgrounds, and less mess, especially when you use magnetic fingerprint powder.
Good castings allow for detailed comparisons between the casting and the known evidence (the shoe). Footwear comparison is similar to the comparison of latent fingerprints to a known set of prints. The Shake-N-Cast™ line of casting materials made by Sirchie® allows both the investigator in the field and the teacher to achieve good castings.
Shake-N-Cast™ consists of a premeasured amount of dental stone casting material packaged with a premeasured amount of water contained in an internal bladder, all as a self-contained unit. The user breaks the bladder and mixes the material within the container. Once mixed, it is easy to pour and evenly distribute the material in the footwear impression. Blue and green versions of Shake-n-Cast™ provide a visual cue, making it easier to properly mix the casting material. The better the cast, the greater opportunity to determine a match.Students should have the opportunity to practice proper techniques using the same CSI and forensic tools used by experts in the field. Exposing students to these techniques and tools now will help to inspire their confidence as they move forward to advance justice.
Recognition and documentation of bloodstain patterns can help establish the pattern of criminal activity during the commission of a crime. These investigations involve the use of trigonometry to determine the angle of incidence. Proper measurement and analysis can determine what happened in these often complicated cases where bodily harm or death has occurred.
Reconstructing crime scenes where firearms were used is an exercise that relies on trigonometry to determine angles of convergence and non-convergence to determine where shots were fired. This type of investigation helps to determine how many shooters were involved, where they were located, how tall they were, and more.
Footwear evidence is the most frequently overlooked type of evidence at crime scenes. Properly identified and matched footwear evidence can be critical to placing an individual at the scene. Getting your forensic students to think about footwear evidence as they approach, document, and process crime scenes will help them become better investigators.
In the field, casting footwear impressions is a valuable skill. Dental stone has proven to be a versatile and highly effective medium if used properly. The benefits of dental stone include higher tensile strength rated in pounds per square inch (psi) and lower expansion rates for a more accurate casting.