Final answer:
Failing to secure the crime scene can lead to contamination of the evidence through inadvertent touching or altering of the evidence by unauthorized individuals, degradation or loss of biological evidence due to environmental factors, and misplacement or mishandling of evidence if not properly documented and stored.
Step-by-step explanation:
Failing to secure the crime scene can lead to contamination of the evidence in several ways. For example, if unauthorized individuals are allowed access to the crime scene, they may inadvertently contaminate the evidence by touching or altering it. Additionally, if proper measures are not taken to protect the crime scene from environmental factors such as weather or animals, biological evidence like blood or DNA can become degraded or lost. Furthermore, if the crime scene is not properly documented and evidence is not collected and stored in a controlled manner, there is a risk of misplacing or mishandling crucial evidence.