You've probably seen one of those stereotypical crime drama TV shows. You know, the ones where the clever cop protagonists show up to the cordoned-off murder scene, pull out some high-tech tools, and suddenly find a miraculous clue in the blood patterns that leads them straight to the killer. It's all Hollywood nonsense, right? Well, maybe not as much as you'd think.

Bloodstain pattern analysis, also called BPA or blood spatter analysis, is a very real tool that crime scene investigators (actual CSIs, not the sunglass-wearing TV kind) use to understand violent crimes. This technique can help investigators determine crucial details about the crime, such as when it happened, what type of weapon was used, and how long the victim survived after the attack.

Scientists often use trigonometry to determine blood spatter impact angle. You won't see that on TV.

The process of BPA has been fictionalized and romanticized by the TV show Dexter, among others, but the fact remains that it's a valid technique used by crime scene analysts.

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So, as a survivalist, why does this matter? First of all, in an urban disaster scenario, rioting or other large-scale violence may take the lives of innocents who end up beaten, stabbed, or shot in the street. By remembering the basics of bloodstain pattern analysis, you can quickly ascertain important facts about scenes of violence you come across. For example:

• Approximately how long ago was the person killed?
• How many perpetrators may have been involved?
• What sort of weapons were used on the victim?
• Was there a struggle, or was the victim ambushed?
• Which direction did the perpetrators come from, and where did they leave?

BPA can assist in answering all these questions. Even if you're not certain what transpired, making an educated guess about the facts of a crime can help you avoid violent criminals, and thereby avoid becoming the next victim.

Here's a useful infographic about bloodstain pattern analysis:

Obviously, if you're looking to prove your analysis in a court of law, you'll need to study BPA for years and become a true expert. However, if you're looking to determine what likely happened at a violent crime scene, and want to prevent it happening to you in the future, a very basic understanding of bloodstain pattern analysis can be a useful survival tool.

Written by Patrick McCarthy