The popularity of high-tech crime-solving shows such as CSI, Law & Order and their assorted spin-offs has dramatically increased public awareness of the role that science can play in solving crimes and gathering evidence that can be used to help convict the perpetrators. But the fictional investigators' real-life counterparts have found the newfound visibility of their profession and its tools to be a mixed blessing. In Ohio, a murder suspect who was also a CSI fan apparently knew enough to use bleach on his hands, which would destroy blood and DNA evidence. Jurors, in turn, are sometimes puzzled when the prosecution's scientific experts carefully qualify their findings with "similar to" or "consistent with," rather than speaking with the nonchalant precision that usually occurs only in a scriptwriter's imagination. A recently published study by Arizona State University psychologists found that regular viewers of CSI and similar shows actually were more skeptical of scientific evidence than non-viewers. In any case, for those who might confuse TV crime solving with real-life investigative work, here are some key differences:
1) TV forensic scientists sometimes carry guns, interrogate suspects, and make arrests. In real life, they usually are civilians without police powers, and work strictly with physical evidence.
2) On TV, stylishly dressed forensic scientists never get messy. In real life, as one actual forensic scientist wrote in an online professional newsletter, "After several hours on the scene it looks like I have taken a bath in fingerprint powder."
3) On TV, the results of DNA tests are available almost instantly. In real life, even the quickest DNA testing method, polymerase chain reaction (PCR), generally requires at least 48 hours to produce preliminary results. The more accurate restriction fragment length polymorphism (RFLP) method can take weeks to months to yield results.
4) On TV, investigators quickly retrieve intact stray bullets from the crime scene. In real life, bullets often become severely deformed or break up into fragments, and they must be removed from a wall or an object with exacting care, so that they won't be further damaged and become unusable. Often, this is done only after other on-scene work, such as determining the angle of fire, is completed.
5) On TV, detectives sometimes pick up a weapon with a handkerchief or by inserting a pencil in the barrel. In real life, the handkerchief might contaminate possible DNA evidence, and the pencil would destroy microscopic markings inside the barrel, making it difficult to match the weapon to slugs retrieved from a victim's body or a crime scene. Instead, one expert recommends holding a weapon in place with gloved fingertips and sliding a thin, stiff sheet of plastic beneath it.
6) When a TV investigator lifts a print from a crime scene, a computer invariably comes up with a conclusive match to a suspect. In real life, automated fingerprint database systems only show the probability that a fingerprint may be a match, and often are calibrated to generate a list of possible matches. Usually, the results are studied by an actual human, who makes the determination. Even then, the match isn't always conclusive. In 2004, for example, an FBI computerized fingerprint analysis erroneously identified an Oregon attorney as a participant in the Madrid terror bombing. He was freed after Spanish fingerprint examiners identified the print as belonging to someone else.
7) On TV, medical examiners autopsy bodies with healthy complexions and handsome features. In real life, corpses often have badly swollen faces and gray, waxy skin. The latter usually is marked in places with hideous purple discoloration known as livor mortis or postmortem hypostasis, which is caused by stagnation of blood in the vessels.
8) On TV, forensic scientists pour caulk into a stab wound on a corpse, let it harden, and then remove a perfect cast of a knife. In real life, the soft tissue around the wound usually is carefully dissected, layer by layer, to create a three-dimensional representation.
9) When TV medical examiners do a show-and-tell for detectives with a murder victim's chest X-ray, watch closely. As a real-life medical examiner once pointed out in a New York magazine article, the heart is often visible on the right, which means the image is in the viewing box backward.
10) TV police routinely magnify and enhance blurry, dark photos or surveillance video images to reveal faces, license plates and other details. While computer-aided enhancement is possible, going to the extremes achieved by fictional technicians probably would turn a digital image into an indecipherable mass of pixels.