For many reasons a teacher may want to utilize the inquiry method of crime scene investigation and forensics but without the theme of an egregious event. For this reason the storyline of numerous CSI and forensics activities have been adapted for a more innocent world. Soil Analysis is for the Dogs is one such activity.
The challenge in Soil Analysis is for the Dogs is to discover which dog dug in a garden through study of hypothetical soil samples collected from the paws of imaginary dogs. The setting is an average neighborhood. The crime scene is your neighbor’s small garden plot. The crime: destruction of a vegetable garden through the thoughtless digging of a local K9. Unfortunately, the victim discovered the damage after watering the garden thus destroying any paw print evidence (but that tangent could be available if desired).
Naturally your neighbor accuses your dog of the crime because witnesses have placed him at the scene of the crime in the past. Your dog also has multiple priors along with a few parole violations. However, while you admit your dog’s had more than a few brushes with the law, he is innocent of this particular misdemeanor. Can you prove it by finding the real culprit?
The materials needed are basic: small plastic bags of soil samples collected from the paws of five imaginary dogs. Each sample is distinct soil type possibly varying in composition, color, particle sizes, and proportions of sand, dirt and organics. A sample of crime scene dirt is provided as well. Samples can be collected easily from any diversity of ground sites around the school or home, or the soils can be manufactured with the desired ingredients. At this point, the difficulty of this activity can be scaled to the students’ talents, grade level, or lesson objectives. The greater the contrast between samples, the easier it is too tell the difference. Instrumentation is also a variable such as if naked eye observations will work, or if magnification, chemical analysis (think vinegar and baking soda), or mechanical separation (think iron filings) will be needed to contrast the samples. Even UV inspection (think UV glow-germs powder) has potential. To add some humor and history to this activity, brief biographies of famous dogs can be included in the sample bag including those of Lassie, Laika, Sergeant Stubby, Snuppy, and Balto.
With samples in hand, the students will need to describe the similarities and differences between each sample compared to the crime scene soil. Depending upon the objectives of the activity, the responsibilities of the students can vary from almost passive observers, through active participants collecting and preparing the samples, even playing the role of expert witness defending the methods, procedures and probabilities of their findings. Should the teacher want to introduce some well-placed monkey wrenches into the mix, complex scenarios can be introduced including the dirt in the neighbor’s garden actually came from a hole dug in your yard last year for a cement walkway (a good plot line for chemical analysis), or the garden plot is actually stratified layers of local and purchased dirt and compost. In this latter case, the samples might differ in only one or two small but distinct parameters.
The activity concludes when the students feel they have enough hard evidence to place one particular dog at the crime scene…unless there was more than one dog involved in the crime.
By Martin Horejsi
