Crime scene investigators must ask the right questions quickly in an effort to gather information about a crime before memories begin to change. Whether the crime scene involves murder, assault, burglary or any number of criminal offences, the crime scene investigator has a very small window of opportunity to interview witnesses on the spot. The longer the investigator takes with each witness, the more frustrated the other witnesses are likely to be because they are essentially detained until they can be questioned. The more efficient the crime scene investigator works in gathering vital information right away, the faster and more effectively he can get to the rest of the investigation process.
Who was the perpetrator? Who was the victim? These are very basic questions that are essential to the investigation process. The crime scene investigator has to learn whether witnesses were acquainted with the perpetrator or victim, or possibly both. When the perpetrator is unknown, witnesses may hold important information that could help identify or narrow down suspects. A CSI must identify details such as height, weight, skin tone and complexion, race and gender, hair colour, eye colour, mannerism, voice and anything witnesses may have seen, heard or picked up during the crime.
What and How
What happened? What was taken, if anything? How did the events of the crime unfold? These questions help investigators uncover possible motive for the crime while attempting to understand what the perpetrator was doing or trying to do. In the case of assault or murder, witnesses may report having overheard an argument or observing a fight. If the incident was a burglary, anything stolen or missing may lead the investigation to suspects. Not every witness will have been observing the entire incident, so investigators have to piece together what happened by comparing and combining the accounts of the witnesses with evidence from the crime scene and possibly the aid of a forensic psychologist.
Encouraging Details without Leading
Leading questions can alter the information witnesses present. It's extremely important for crime scene investigators to avoid jumping to conclusions before gathering information. This can lead to investigator bias, in which the investigator is only seeking information that confirms her suspicions. Objectivity is the key to solid, accurate police investigations. When interviewing witnesses at a crime scene, the interviewing investigator can encourage details by asking follow-up questions such as, "And then what happened?" or "How can you be sure that is what you remember seeing/hearing?" These questions encourage the witnesses to find the details within their own memories of the incident. Leading questions would point to information the witnesses may not have or cause the witnesses to recall inaccurate details that support what the investigator is saying or asking for.
Witness Contact Information
All witnesses must present contact information before being dismissed from a crime scene. This information is vital for the investigation process as well; many witnesses may need additional questioning or provide assistance with police line-ups for identifying perpetrators. Occasionally, however, witnesses provide misinformation that makes contact difficult for the investigators later. A thorough crime scene investigator verifies witness information before dismissing witnesses.