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Victimology is the collection and assessment of any significant information as it pertains to the victim and his or her lifestyle. Investigators must know the victim and complete a victimology study on every suicide, you cannot properly investigate a death without it.
Ultimately you need to find out, in detail, who the victim was and what was going on at the time of their death. The best source of information will be friends, family, employers, and neighbors. Your goal is to get to know the victim better than they knew themselves.