Cincinnati-area experts explain how they analyze crime scenes with a mix of high-tech and old-fashioned tools.
Order From Chaos
Investigators strive to keep a crime scene as undisturbed as possible while collecting evidence. Anyone who enters the crime scene is recorded, and anyone who touches the evidence is listed on a chain of custody form. Collecting the evidence can vary; photographs will definitely be taken, and all original evidence will be removed if possible—including things you’d expect (the handgun used in the crime, the victim’s clothes) and things you might not (drywall with blood spatter patterns, random bits of hair or tissue, dusty footprints, even chipped or broken floor tiles).
There’s usually blood at a violent crime scene, but biohazards and dangerous substances like drugs and used syringes can be found there as well. Investigators and lab personnel carry Narcan to revive anyone who has overdosed, including police who might accidentally come into contact with lethal doses of drugs just by breathing or touch.
Using high-resolution cameras and video, police department techs can record the entire crime scene, start to finish, and conduct audio/video witness interviews. Drones now help out by making aerial maps of traffic accidents, with the hope of using them for search and rescue one day.
If a death occurs at the crime scene, it isn’t long until houseflies find their way to the body, followed by ants and wasps, which eat the flies. Investigators count and collect the bugs for study by the forensic entomologist, who uses them to help determine the time of death and the presence of drugs or poisons.
Myth of Fingerprints
Contrary to popular belief, finding a fingerprint match doesn’t mean “case closed.” Usually, there are only partial prints left at crime scenes, which can match hundreds of people in the federal AFIS identification system. Dirt, debris, and excess powder can make the print less recognizable.
Investigators hardly ever draw chalk outlines at a crime scene. The only situation that would warrant one is if the body needed to be removed faster than usual; numbered flags would likely be used instead to keep contamination of the crime scene to a minimum.
Finding ways to recover digital data from computers and cell phones can be invaluable for investigators.
Specialized chemicals such as Luminol or Blue Star are formulated to react to the presence of blood, even after it’s been cleaned up. The reaction is visible under ultraviolet light, which can then be photographed for evidence collection. That’s usually done last, as the reaction destroys DNA.
When a gun is fired, distinctive ridges are etched into the bullet casing that are unique to that particular gun, creating a distinctive pattern that can be used as a fingerprint for the gun. These ridges are studied under a comparison microscope, photographed, and uploaded to a database called NIBIN, a national system for guns that’s similar to AFIS.
Too Many TV Cop Shows
Everything takes time, especially criminal investigations. TV shows tend to speed up the process for entertainment value; in reality, collecting and testing evidence can take days or weeks.