How Is DNA Evidence Used in Arson Cases?

Video Transcript

"If you've ever watched an old detective movie, you might see them dusting for fingerprints or canvasing the town looking for an eyewitness. Fingerprints and eyewitnesses used to be considered top notch evidence in criminal cases. But nowadays they look for something even more. Hi I'm Janice Crenetti. I've been teaching biology for over 20 years and I'm here to answer the question, how is DNA evidence used in arson cases? Well not just arson cases, but really any criminal investigation. DNA evidence is now considered one of the absolute best ways to prove whether or not somebody could have been the person who committed a crime. And to confirm that yes, this person's blood or hair sample matches what was left behind at the crime scene. Well what exactly is DNA first of all? Well DNA is the genetic material that's inside the cells of your body. It's kind of like the blueprint or the recipe for determining who you are. You see, your DNA is different than everybody else's. The only people on the planet who would have identical DNA would be identical twins because they came from the same fertilized egg so they have exactly the same genetic material. Well DNA is found inside of body fluids, inside of hair, inside of blood. So a detective can get a sample of someone's hair or blood left behind at a crime scene. They can extract the DNA from the cells and they can create something called a DNA fingerprint. That's what I have behind me. Basically what happens is they cut the DNA into little segments using enzymes and then they apply electricity to the solution. DNA fragments that are short move farther. DNA fragments that are heavy don't move so far. Well someone's DNA fingerprint, like I said is going to be unique to them because their DNA pattern will be unique. So if this DNA fingerprint matches the DNA fingerprint that was left behind at a crime scene, you can say without a doubt that this person had to be there because no one else is going to have their exact fingerprint. DNA evidence is really revolutionizing the way that criminal cases get investigated. DNA evidence is even helping to get people off death row that have been falsely accused. It's an amazing technology that we're using for a whole lot of good in the human society. I'm Janice Crenetti and this is how is DNA evidence used in an arson case."