An Engaging Lesson Model for Biological Evidence Collection Training for DNA

Abstract

According to the Locard’s Exchange Principle, “every contact leaves a trace.”  The study of touch DNA further explores this principle: when a person comes in contact with any surface, they will leave residual evidence behind.  Touch DNA is a common form of evidence but may be difficult to recover and to obtain genotyping information from.  Factors thought to affect the transfer and recovery of touch DNA include duration of contact, surface type, genetic “shedder status,” environmental factors (e.g. heat, humidity), bacterial action, DNA degradation rate, pressure applied to surface and recovery method (e.g. swabbing, cutting, tape lifts).  Here a college-level lesson uses cell biology and programmed cell death (apoptosis) with a set of touch DNA exercises to serve as an example of experimental design and training on DNA contamination in forensic science.  This lesson plan utilizes student learning activities, students collect data to authenticate beliefs, and translate the information for biological evidence collection strategies and discussion.  The activities are divided into two categories: microscopy with cytology, and human identification by DNA. Both categories are relevant to biological evidence collection training and methods.  This lesson can be useful for training workshops and forensic science, cell biology and basic biology college courses.