Because forensics is such a hot topic these days, millions of viewers are becoming armchair experts on that subject. But is Hollywood reliable? Sometimes yes, sometimes no.
The quick death
A gun is shot or a knife is thrown and down goes one of the bad guys, perhaps clutching his chest or taking one last dramatic breath, but either way, he's instantly a goner.
The problem: No one dies instantly in those circumstances. Well, almost no one. Instant death can occur from heart attacks, strokes, extremely abnormal heart rhythms, and with cyanide and other metabolic poisons (toxins that perform their mischief inside the cells of the body).
Trauma from gunshot wounds (GSWs) and knife wounds, however, rarely causes instant death. Yet, how often has a single shot felled a villain? Bang, and he drops dead. For something like that to occur, the bullet would have to severely damage the brain, the heart, or the cervical (neck) portion of the spinal cord. A shot to the chest or abdomen normally leads to a bunch of screaming and moaning, but death comes from bleeding, and that takes a while.
The pretty death
In the Hollywood Death, the actor looks calm and peaceful, and not a single hair is out of place. And what about blood? Not a drop. Well, unless it's a Freddie or Jason slasher movie, where blood is almost another character unto itself. The deceased is often nicely dressed, lying in bed, with perfect makeup and a slight flutter of the eyelids when you look closely. This description is particularly true when the deceased happens to be one of the good guys.
Face it: Real dead people are ugly. It doesn't matter what they looked like during life. In death, they're pale, waxy, and gray. They have dead-looking eyes, dark-blue lividity, and pale faces. Their eyelids don't flutter, and they don't look at all relaxed and peaceful. They look dead.
And fairly quickly they smell bad. When a movie detective ventures into the Louisiana swamp and finds the girl who's been missing for four days, she might be damp and dirty, but she's still beautiful. How else can the audience sympathize with her demise? The fact that she's been lying in a wet, 90-plus-degree environment for four days seems to make little difference in her appearance. The facts: They'd smell her before they saw her, and she'd appear something less than pleasant.
The bleeding corpse
A detective arrives at a murder scene a half hour after the deed and sees blood oozing from beneath a door. When the detective pushes the door open, a corpse lying on the floor oozes blood from the mouth and from the gaping GSW in the chest.
TILT! Blood clots within minutes of leaving the body and, surprise, dead folks don't bleed. When you die, your heart stops, and your blood no longer circulates. When blood stops moving, it clots, and, you guessed it, clotted blood doesn't move. It doesn't gush, ooze, gurgle, flow, or trickle from the body, and it neither oozes beneath a door nor flows from a wound.
The exact time of death
How many times have you seen the detective or the ME confidently announce that the victim "died at 10:30 last night?" Exactly how did the ME make that determination?. Was it rigor mortis, body temperature, or lividity? Was it the presence or absence of certain bugs? Of course, the problem is that none of these forms of evidence reveal an exact time of death. Each of them may provide an estimate of the time of death, but not even a combination of these factors enables the ME to exactly pinpoint the time of death.
In real life, the ME says that the death "likely occurred between 8 p.m. and midnight." But that obviously makes the ME appear wishy-washy, and Hollywood likes its heroes to be smart — sometimes even smarter than they can possibly be.
The one-punch knockout
The hero socks the bad guy's henchman in the jaw. The henchman goes down and apparently is written out of the script because you never hear from him again. It's always the henchmen because antagonists, like most real people, require a few solid blows to go down.
For a little perspective, think about a boxing match. Boxers are guys who are trained to inflict damage, and even they have trouble knocking each other out. And when they do, the one on his back is up in a couple of minutes, claiming the punch was a lucky one. James Bond may be able to knock someone out with a single blow, but real people (with the possible exception of Mike Tyson) can't, and neither can a car salesman turned amateur-sleuth or a recovering-alcoholic, cigarette-smoking private eye.
The disappearing black eye
The beautiful, made-for-TV movie actress is subjected to a pop in the face from the bad guy. In the next scene, she hides her obvious black eye behind a pair of sunglasses, but in the following scene, there she is again, back to her porcelain-complexioned self.
The reality is that a character who gets a black eye in Act 1 has it for two weeks, which likely takes you a long way past the end of the movie. That character can't look normal later that day in Act 2.
A black eye is a contusion (bruise) caused by blood leaking from tiny blood vessels that are injured by the blow. Your body takes about two weeks to clear all that out of the tissues. After you're hit, the resulting bruise darkens for about two days, fades during the next four or five days, and turns greenish, brownish, and a sickly yellow before disappearing.
The fast-acting poison
Within seconds of drinking arsenic-laced tea, a concerned, then frightened look comes across the victim's face, she clutches at her throat, and falls dead. Very dramatic. Also, very unlikely, but that hasn't stopped it from being a Hollywood staple for decades.
Acute arsenic poisoning doesn't kill that quickly. In fact, it may take several days. The victim develops sudden abdominal pain, nausea, vomiting, and possibly bloody diarrhea. Not a pleasant visual, so it's better to simply portray victims grabbing their throats and then collapsing.
In the age of terrorism, you've probably become familiar with several other fast-acting toxins: sarin and VX gas, for example. However, these substances are hard to come by, and most readily available poisons work much more slowly and don't cause a sudden collapse and death.
The untraceable poison
The clever big-screen evildoer gets away with murder by using a poison that doesn't leave a trace of evidence. No such thing.
A diligent search by the forensic toxicologist can reveal traces of virtually any chemical or its metabolites. With fancy equipment like gas chromatography/mass spectroscopy (GS/MS), forensic scientists can determine the fingerprint of virtually any chemical. Because the Hollywood poison is untraceable, there's no need for an expensive and time-consuming full toxicological examination.
Another common scenario is for the ME to find a strange and unusual poison in about 20 minutes. Sorry, folks, it just doesn't work that way. First, the ME must use screening tests to determine whether a poison is present, and if so, what type of poison it is. The ME then uses more definitive testing, such as GC/MS, to identify exactly which poison is present. These processes take time.
The instant athlete
The hero chases the bad guy down streets, over bridges, through tunnels, up stairs and ladders, and over fences and rooftops, barely breaking a sweat or breathing hard, and certainly without a hair out of place. More often than not, the hero is a cop or a private investigator who drinks too much, smokes too much, rarely sleeps, and eats donuts on a regular basis. You see the hero in disheveled clothing, not gym attire. You see the hero sitting in a bar, not pumping iron or running on a treadmill. When you're out of shape, adrenaline takes you only so far — a block, maybe two on a good day. The same goes for the bad guys.
The high-tech lab
Beautiful people stroll through one high-tech, sleek-looking lab after another, solving crimes (involving more beautiful people) with the newest and best equipment and at lightning-fast speed. That's how it works on TV, but the real world is not like CSI. Visit your local crime lab, and you don't see plasma-screen TVs, top-of-the-line computers, or beautiful people. The personnel in most crime labs are beautiful for the incredible and often thankless work they do, not necessarily because they have pretty faces.
Real labs are likely to be in windowless basements of police departments, where the norm is institutional green walls and secondhand, patchwork equipment held together with spit and chewing gum. Such are the budgets of most labs.