During a murder investigation, a detective must answer the following three questions:
- Motive: Who had a reason to kill the victim? Did any particular person benefit from the victim's death?
- Means: Who had access to the murder weapon and victim? Did any particular person have the unique knowledge, skill or physical ability necessary to use the murder weapon?
- Opportunity: Who had a chance to kill the victim? Is any particular person unaccounted for (has no alibi) during the time the victim was killed?
