What standard is needed to justify an arrest?

The standard needed to justify an arrest is probable cause. This means that law enforcement must have a reasonable basis for believing that a crime has been committed or that a particular individual is involved in criminal activity. Probable cause goes beyond mere suspicion; it requires facts and evidence that would lead a reasonably intelligent person to believe that a crime has likely occurred.

In contrast, visual confirmation of a crime may provide evidence for probable cause, but it is not strictly required in every situation to justify an arrest. Similarly, the presence of multiple officers may enhance officer safety or provide backup but does not directly affect the necessity for probable cause. Lastly, collecting witness statements can constitute important evidence but is typically part of gathering information to establish probable cause rather than serving as the standard itself.