In most cases, which layer(s) of soil is/are picked up during the commission of a crime?

The top layer of soil is the most commonly picked up during the commission of a crime for several reasons. This layer, also known as the "surface layer," is where most environmental interactions occur, including the presence of organic materials, plants, and human activity. It is the most disturbed layer due to regular activities such as walking, driving, and landscaping, making it the most likely to be transferred to a suspect's shoes, clothing, or belongings.

Additionally, the top layer is often more heterogeneous, containing various materials that can provide critical evidence, such as pollen, seeds, or human-made debris, which can help link a suspect or victim to a crime scene.

While subsoil and bedrock may contain relevant information, they are generally deeper and less likely to be disturbed in a way that facilitates transportation during a crime. Therefore, the top layer is the most relevant in criminal investigations concerning soil evidence.