Which of the following must be recorded upon arrival at a crime scene?

The requirement to record your time of arrival and the weather conditions upon arriving at a crime scene is crucial for several reasons. Documenting the time provides an accurate timeline of the investigation, which is essential for understanding the sequence of events, as well as for maintaining the integrity of the evidence. Knowing the weather conditions is equally significant, as it can influence both the crime scene itself and the behavior of witnesses or suspects. For instance, poor weather might affect visibility or mobility, which can impact witness accounts or even the preservation of physical evidence.

The other options do not carry the same level of necessity upon arrival. Recording the time of departure from the police station may offer some context, but it does not directly pertain to the crime scene itself. Similarly, while it's important to identify witnesses later in the investigation, their names are not required to be logged immediately upon arrival at the scene. Evidence discovered before securing the scene should also be recorded, but it is generally advisable to secure the crime scene first to avoid contamination, making this less relevant at the onset of arrival. Thus, the emphasis on documenting your time of arrival and weather conditions highlights the foundational steps essential for a thorough and effective crime scene investigation.