A teacher is dead on her bedroom floor, hands bound and head caked with blood from a gaping hole. Soon, glamorous and clever crime-scene investigators clad in latex gloves swoop onto the scene, painstakingly scraping hair and fiber particles into plastic bags and quickly discovering an errant bullet casing forgotten under the bed.
Back at the high-tech lab with moody lighting, slides are analyzed under fancy microscopes, forensic tests are conducted. And within an hour, the perp is arrested.
Makes for great TV, but working as a real-life crime-scene investigator is far different from the way it’s often portrayed in crime dramas. Here are some of the biggest misconceptions about being a CSI, according to actual crime-scene experts:
If a CSI Finds Your DNA, You Must Be Guilty
Lots of criminals leave behind fingerprints, blood, hair or other evidence indicating they were there, but that’s not enough to prove culpability, says Tim Palmbach, chair of the forensic science department at the University of New Haven and a former major in the Connecticut Department of Public Safety’s scientific services division.
The DNA of an innocent person such as a family member, friend or even a visiting service technician is frequently discovered at a crime scene because that person was present for a legitimate reason. “It is often a complex task to determine how much they correlate,” if at all, he says, so the investigation must continue in order to establish guilt.
On the other hand…
If a CSI Comes Up Empty, a Suspect Didn’t Do It
Not necessarily, Palmbach says. If no usable evidence turns up, it could mean a crime scene was processed improperly, the lab performed inadequate tests or returned inconclusive results—or even that the suspect managed to cover his or her tracks so carefully that no forensic evidence could be detected, he says.
Though the public has become conditioned to expect “absolutely off-the-chart ideal scenarios,” he says, that’s something “we rarely achieve.”
Fingerprints Aren’t Hard to Obtain
In actuality, they can be surprisingly difficult to get, says John Paolucci, a retired New York Police Department detective sergeant who also served as a crime- scene unit supervisor.
During his tenure, it wasn’t uncommon to see a 5 percent success rate in retrieving prints from firearms, while those on shell casings are “very difficult, almost impossible to develop, even in laboratory conditions,” he says.
Despite difficult conditions, however, fingerprints can be found—just not as easily as they are on TV, says Marilyn Miller, an associate professor of forensic science at Virginia Commonwealth University and author of several crime-scene textbooks.
For example, she says, “There’s a prevailing belief that you can’t get fingerprints off a wet surface.” But with specialized chemicals and techniques, “you sure can,” she says. She recalls the time cops were after a mail carrier who had tossed letters into a drainage ditch. She retrieved the damp mail and was able to find the mailman’s prints on the envelopes, helping prove their case, she says. Another time she discovered fingerprints from a still-wet car that had just been pulled out of a lake.
It’s easier to obtain wet prints from non-porous surfaces like a gun thrown into a pond, but even with porous items like water-logged money, cardboard boxes or paper notes, she says, “the proteins in the fingerprint will produce a dark color.”
A CSI Nabs Just One Piece of Evidence and the Case Is Solved
In fact, the more data, the better. “When you see it on TV, they walk in and find the greatest piece of evidence,” Paolucci says, but in fact, “There is [usually] no one smoking gun.” Every little bit of proof helps, according to Paolucci, including police body-cam footage, video from surveillance cameras, computer files and other digital media… “They’re all pieces of the puzzle,” he says.
Paperwork Is an Afterthought
The truth is that real CSIs spend a significant part of their jobs filling out reports, evidence receipts and other documents, says Miller, who previously worked as a forensic scientist for law-enforcement agencies in North Carolina, Pennsylvania and Florida. “Of course you spend a lot of time afterward at the office,” she says. “Writing the paperwork is a bit of a drag, but that’s part of the job.”
Blood Lights Up Under Ultraviolet Light
Actually, not only does blood not fluoresce (glow) when UV light is shined on it, it darkens, Paolucci says. However, body fluids that do light up with such illumination include semen, saliva and sweat.
Crime Scenes Are Easy to Keep Pristine
Definitely not. “Every single crime scene is going to get contaminated,” Palmbach says, attributing that reality to the flurry of activity that ensues in the aftermath of a crime. Numerous people are typically coming and going, including law-enforcement officers, medical personnel, crime techs, witnesses, family and sometimes gathering crowds.
First responders might pick something up and move it, inadvertently smudge a fingerprint or smear a blood stain, he says. “You’re going to step on another footprint,” Palmbach says, “You’re going to kick evidence.”
Most Evidence Is Contaminated, Preventing Its Admissibility in Court
It is rare to find a completely sterile scene, Paolucci says. But perfection isn’t necessary to bring the evidence to court. And if a question arises about a specific item, “you can go back afterward and collect” proof detailing the cause. One police department he works with, for example, has first responders and others at a scene submit photos of their shoes so CSIs can rule out known shoeprints, he says.
CSIs Perform Their Tasks In an Hour, Maybe Two
Nope, not usually. “It’s way longer than you think,” Palmbach says. “The shortest time we ever spent was two hours (at a homicide scene) and it was nightmare. We left so much behind.”
A typical murder scene takes eight to 10 hours to process but “it’s not uncommon to go 30 to 35 hours,” he says.
Just One CSI Collects the Evidence, Studies It at the Lab and Interrogates Suspects
In truth, those jobs frequently are done by separate people who “have nothing to do with each other,” says Palmbach, who also testifies as expert witness on crime-scene reconstructions. “Those are three different careers with three different levels of training.”
Investigators Live Glamorous and Exciting Lives
Maybe, but usually not at the heightened levels portrayed on the screen. “They’re always showing up in high heels,” Miller says with a laugh of the women CSIs on TV. In fact, investigators tend to wear more utilitarian outfits that don’t include lovely, but impractical, footwear.
“I can’t tell you how many pairs of shoes I’ve ruined walking through water or mud to find a piece of evidence,” she says.
Meanwhile, personal relationships do occur, but “they’re more salacious on TV,” she says of work romances and entanglements. “That was always a good subplot, but that’s not reality.”