The Forensics of Horror Part I: Vampires

In honor of October, this month's posts will focus on the forensics of horror. Never underestimate a scientist's ability to find science everywhere!

The other night I was watching a truly terrible vampire movie. It was truly bad. Tears from laughing, bad.

Anyways, at one point the vampire hunter "hero" (I put hero in quotes because I love vampires, I always root for them in the movie) sits next to a girl in a bar who starts talking to him almost immediately. Soon...she says something that sounds very suspicious. This alerts our "hero" that something is up. He excuses himself and from the corner, starts scanning the bar with his infrared scope. Person after person shows red with a temperature reading of 98 until we reach our girl at the bar...who shows BLUE with 41 as her temp!

No. No. NO!

There are two problems with this scenario. One I can forgive and one I can't.

#1: Every single human shows 98F. Without exception. 

98.6F is the average human temperature. As anyone who has looked at statistics with any amount of attention will tell you, there is always some variability to an average. With human body temperature there is actually very little variability. It's not as if some people have a 50F temperature and another has a 147F temperature, and the average is 98F. No, humans are around 98F because there is a very small range that allow a human to survive and function. Even still, some healthy people have temperatures of 97F (yours truly) and others of 99F and that is fine. Ok, we'll forgive the movie this one. Perhaps his scope doesn't have the greatest sensitivity to differentiate that.

#2: The vampire is 41F.

NO! I should point out at this point that our characters are in New Mexico. They are wearing t-shirts and light jackets so we can safely assume ambient temperature is around 70F or so, but the vampire is so cold, she may have walked out of a fridge. Unforgivable!

Unfortunately, this error is repeated time and time again in any story where vampires are present. Movies, books; even the very, very popular Twilight series makes this error throughout the series. The couple even go to a tropical island where our vampire lover acts as a type of air conditioner for his human wife. No, No, NO!

Let me explain: The theory behind this is that vampires are dead and corpses are "cold" so vampires are cold, thus 41F is acceptable. Scientifically speaking, that doesn't fly. (Yes, I realize we're arguing science in fantasy, but we're going to do it anyway.)

The reason a corpse is cold to the touch of a living person, is that, as stated above, our temperature runs around 98F. Anything cooler than 98F feels cold to the touch. Don't believe me? Touch a part of our desk that you're not touching right now. Cool to the touch right? A dead body is one in which all metabolic processes has ceased (or are as close to stopped that they might as well be). The body is no longer producing heat and so begins to cool to ambient temperature. If the room is 65F and a person dies in it, they will begin to cool from their 98F starting point to room temperature.

This is important because in forensics, time is very important. It doesn't matter if it's a DUI, a sexual assault or an overdose. When it happened matters. We must have a time-line to the best of our ability. One of the ways to tell how long a person has been dead, is their body temperature. Bodies cool at a certain rate. This rate of cooling can be affected by several factors including ambient temperature and their condition prior to death. Even with those factors, an examiner can use body temperature (assuming it is above ambient) to provide a window for the time of death.

The important point are these words: "the rate of cooling." Cooling. The body is cooling from 98F to ambient temperature because it is no longer producing heat. This lack of heat production means the body cools. The body is not producing cold. The morgue is cold (parts of it) because the bodies are refrigerated, it is not because the corpses are producing the cold to air condition the place. That's just silly.

If a corpse was being examined and it's body temperature was 41F we would have to assume that either it was found outside in winter or the body has been refrigerated. (Or perhaps the body was frozen and now it is warming to room temperature.)

So, if vampires are corpses and that is why they are cold then why is our vampire 41F in New Mexico? She wouldn't be. She would be ambient temperature if we assume that vampires do not produce their own heat. Our movie could have done the same scene and shown the vampire blue with a temperature of 70F and our "hero" still could have been suspicious without destroying any scientific integrity.

Now, to continue the logic that the vampire does not produce heat and will be ambient temperature means that they will also be warm at times. If it were summer time in New Mexico as opposed to winter, our  "hero" could have looked through the scope and seen our vampire at 105F. Not as dramatic, but it could be true. In that case, our southern vampires of the "True Blood" series should be fairly warm in most cases and may even be warmer than the humans, since humans have the ability to cool our temperature as part of our regulation so we don't overheat. Can you fry an egg off a vampire in Death Valley? Maybe. This would also pose some problems for the "30 Days of Night" vampires in Alaska since they would be frozen.

Anyways, I digress. If we are to assume that vampires are cold because they are corpses and corpses are cold, then we must focus on the science. Dead bodies will cool to ambient temperature, but they will not produce cold. Therefore, the movie in this case, and the Twilight series has it plain wrong. Our vamps would be more like 65F (though we wouldn't be able to estimate their time of death.)