Tool Marks Forensic Examination: Methods & Purpose

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  • 0:03 Tools Used in a Crime
  • 1:17 Tool Mark Information
  • 1:58 Initial Investigation
  • 2:28 Preserving Evidence
  • 3:33 Comparison Microscope
  • 4:02 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson is going to go over some of the basics behind tool marks in forensics. You'll learn what tools criminals use, why we examine these tool marks, and the fundamentals of how they are examined.

Tools Used in a Crime

When you think of a criminal breaking into a home through a door, what pops up in your mind? Admit it, a crowbar, right? A crowbar is just one tool used to pry things open, including doors. There are plenty of other tools criminals use and plenty of ways by which investigators try to identify which tools were used during a crime.

Old Vito Siegel is a small time burglar and he's a got an entire arsenal of tools he uses to commit his crimes. One day Vito decides to break into a local store that's closed for the night. He uses some bolt cutters to cut a padlock on the front gate leading up to the store. Then, he sneaks up to the door and uses lock picks to get inside. Once inside, he pries open the door to the office using a crowbar. Inside the office he sees a safe. He tries to use the crowbar, screwdrivers, and a hammer to open the safe but it's not working. So, instead, he uses a blowtorch to burn through the metal safe to get the money inside. Mission accomplished.

The tools Vito used are just some of the many different kinds criminals use. Just about anything you can imagine you'd use to build or fix something, a criminal could use during a crime for their nefarious purposes as well.

Tool Mark Information

Why bother examining the marks Vito left behind? Well, let's think about this logically. Is the store owner going to purposefully destroy their property with tools? Possibly, but not likely. So, a tool mark is a clue to a criminal act in many cases, and it shouldn't be ignored.

That's because that tool mark can carry important information, like the kind and size of the tool that may have made that mark. The marks may also have microscopic evidence, like irregularities, which can help investigators figure out the way the tool is manufactured or used. And all of these features may be linked to a tool that is later recovered during the course of an investigation!

Initial Investigation

Let's say you're the investigator going over Vito's crime scene. There is a lot to consider! For example, you need to make sure the tool marks are relevant. Maybe the store owner really did cut his own lock because he forgot the key! Also, examine any outbuilding, like a shed, to see if any tools were stolen or taken from there to commit the crime. You don't have to drain the pond next door to look for the tools just yet. Record the crime scene with a digital camera a well. Use a scale in the photo as you take the shot.

Preserving Evidence

So let's say you've identified a mark that is important to preserve. What do you do? The best thing you can do is to literally take the item for storage and submit it to a lab. Entire doors and windows have been submitted before! If it's not possible to take the entire item bearing the mark, then the mark should be cast, using materials like silicone.

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