by Tom Adair, forensic scientist
First responders such as paramedics and firemen are heroes. They rush into dangerous and chaotic circumstances at great risk to themselves all for the sake of providing aid. But, as much as I appreciate paramedics and firemen, sometimes they really piss me off. It's the tidy ones that get my goat. You see, when they rush into a shooting scene you expect them to tear open their gauze, unpack needles, and attach defibrillator leads, dropping all their packaging trash on the ground. They can make a huge mess, but it usually pales in comparison to the blood, brains, and other nasty fluids.
Since the scene is already a mess you'd think they wouldn't feel compelled to pick up their trash. Most don't, but every once in a while CSIs run into an anal retentive garbophobic EMT or hose-dragger hell bent on picking up their trash. Taking the US Forest Service mantra, Leave No Trace, literally to the point the CSIs want to kick them in the coconuts. Pardon my French. If it were up to me I'd pass a law requiring fire departments to only hire slobs and employees who clearly demonstrate they prefer to litter.
Why you may ask?
CSIs don't like other people picking up things in our crime scenes; we're kind of selfish that way. We know that if you're picking up "trash" you might also inadvertently pick up things like hairs, fibers, cartridge casings, and who knows what else! I could care less about the packaging to your gauze pad but a spent cartridge casing? That, I care about. You might be thinking that it would be impossible for these professionals to pick up a bullet and not realize it but you'd be very, very, wrong.
I was investigating a double homicide one time, and it was clear that the victims were dead long before paramedics arrived. But they have to be sure and they went through the motions of attaching their defibrillator leads and stuff, creating some trash. Before I got to the scene they declared the victims deceased, gathered up their trash, and headed back to the station house. I'm accustomed to seeing a bunch of medical trash on the ground surrounding homicide victims. I really don't mind it at all. So when I arrived at this scene and saw the tidy appearance I was a bit miffed. A quick count of the bullet holes in my victims (five each) and the lack of the same number of cartridge cases spiked my heart rate to say the least.
To shorten a long story I called them back and found the missing cases in their trash and one casing wedged in the tread of one guy's boot! It all worked out in the end in this case. But what if it hadn't? Scenarios like this are not unheard of in real life. People, even trained professionals, can develop a kind of tunnel vision when performing common tasks. If paramedics respond to ten non-criminal calls in a day and routinely pick up the trash, should we be surprised if they do the same on the 11th call at a homicide?
As an author, you might consider using this reality to create challenges for your characters. Imagine a strand of the killer's hair that was accidentally picked up with the trash and is mixed in with the trash of ten other calls? It would potentially lose all of its legal weight right? Investigators may still use that information to form their own opinions but it may not be admissible in court. It may also create tension between your characters, which can make for some exciting dialog. Play around with some ideas and see if one works for your story.