What is the primary step to take before conducting a showup?

The primary step to take before conducting a showup is to interview all victims and witnesses separately. This approach is crucial because it helps to avoid the potential for witness contamination, where one person's testimony could inadvertently influence another's recollection of events. By interviewing each victim and witness individually, the investigator can gather independent accounts of the crime, ensuring that each person's perspective is preserved without cross-influence.

Conducting separate interviews also allows for a more thorough understanding of each witness's perception of the suspect and the incident. It can reveal inconsistencies or corroborating details that are important for the subsequent identification process. This method plays a significant role in maintaining the integrity of the investigation and the reliability of the evidence collected. In contrast, interviewing all victims and witnesses together can lead to suggestive influences, which may compromise the validity of their identifications.