If you’re writing a murder mystery, you need to know how your investigator will go about solving the crime. The first step is to secure the scene. I’m taking this information from the Whodunit book called Murder one: A Writer’s Guide to Homicide by Mauro V. Corvasce and Joseph R. Paglino.
The first officer at a crime scene is supposed to preserve the integrity of the scene until a supervisor arrives. To throw a wrench into your protagonist’s investigation, you could place a rookie officer on the scene and he doesn’t secure it immediately or completely. Or you could use a corrupt officer. Or you could be nice and get the job done properly, which basically means keeping everyone out. Nothing should be moved, not even the body. Sometimes well-intentioned witnesses can mess with this, like when they roll a body over to check for a pulse, or gather the body in their arms during an intense moment of grief, or try to perform CPR on someone who’s too far gone to resuscitate. These are believable scenarios, as they happen in real life. If they happen before the first responding officer arrives, there’s nothing he can do about that, and the investigator’s job just got harder.
The first officer on the scene should keep bystanders as far away from the scene as possible so they don’t inadvertently (or purposefully) contaminate any evidence left at the scene. This is especially tough if the crime occurs outdoors, where weather, wildlife, and heavy foot traffic could have already messed with the scene before the officer arrived. Again, complications like this make it tougher for the investigator to solve the crime, which in real life is horrible but in fiction is fantastic. There are, of course, limitations to what one officer can do. If it’s raining, he might think it’s a great idea to erect a tarp over the crime scene, but in reality, he could contaminate the scene with his efforts by wiping out footprints or scattering his own DNA over the body. Plus, while he’s trying to erect a tent, people could slip by him to corrupt the scene. So keep these limits in mind when you write the scene. Most of the time, a first-responder is alone or with a partner, and there’s only so much one or two people can do. Their one and only objective is to preserve the scene.
Once a supervisor arrives (usually a sergeant or a lieutenant), the responsibility of crime scene integrity is shifted to them. That first officer can then stay on to help preserve the scene (especially if it’s a messy outdoor scene), or can be utilized in a canvas of the neighborhood searching for witnesses, or he can be sent back on shift. It all depends on the supervisor’s directives.
Here are the main duties involved in preserving crime scene integrity:
1. Surround the area with police tape
2. Control any crowd
3. Keep the media and family members away so they don’t accidentally or purposefully destroy or remove evidence
That last one seems a bit cruel, keeping family members away from their dead loved one, but it’s crucial to the investigation. Remember, most homicides are committed by someone who knew the victim. If a grieving family member breaks through the police tape and cries all over the body, now their DNA is on the body. If the crier was actually the murderer, the investigator can’t use any DNA evidence found on the body as proof of murder.
When writing a murder mystery, it’s always fun to mess with the investigation and make it hard for the protagonist to actually solve the crime, but if you mess up too much of it, the reveal at the end won’t be believable. Play fair with the reader and let them see all the clues necessary for solving the crime. After all, that’s the part I find the most fun in reading mysteries: seeing if I can figure out who did it before it’s revealed at the end.
Come back next time for step two on the procedure’s list.