Science & Tech

Identifying Vulnerabilities: Darrell Gene Devier

John Douglas

Lesson time 11:36 min

John gives us an inside look at the case of convicted rapist and child murderer Darrell Gene Devier. He notes that we all have vulnerabilities—but if you can learn how to identify them in others, you can use them to predict behavior. By understanding Devier’s vulnerabilities, John was able to coax a confession out of him.

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Topics include: Case Study: Mary Stoner • Profiling Mary’s Killer • Staging: Getting a Confession • Assignment


- All of us have vulnerabilities. We have strengths. We have weaknesses. There are times maybe when we let down our defenses. But we have to recognize them. All of us have breaking points. You don't know mine. I don't know yours. Unless you have a close personal friend, unless it's a family member, you may not know what's going on in their personal life. You may not know what are the triggers. In this chapter, I'll help you identify vulnerabilities in ourselves and others, and how they can be used to help predict behavior. The case we're going to be talking about is a case in Adairsville, Georgia. And the victim's name is going to be Mary Stoner, who will be the victim of a rape-homicide. She was a majorette in school. As far as risk level, really low risk level. This ends in a homicide. She's found about 10 miles away. She's back by a tree. She's face-down, has a coat over the top of her. Method and cause of death is blunt force trauma to the head, caused by a stone, about a 45-pound rock that was dropped on the victim's head multiple times. The cops call me up. I'm at Quantico. This is not on-site consultation. It's through Quantico. They give me some of the information and how she was found. And I said, by the way, was she manually strangled? He said, yeah, how did you know? He said, because he didn't really plan on killing her. His fantasy was, he sees this girl who has this reputation of being really friendly. He's misunderstanding. He has a fantasy here. And he's believing that there's some kind of attraction to himself. So he thinks he's going to have a relationship with this girl. So he abducts her. And so the weapon is going to be a weapon of opportunity. But he has to kill her. After he sexually assaults her, walk in her shoes, and see the pain that she was going through, probably regressing, calling back to her mommy, her daddy to help her. Now what is he going to do? He tells her to go walk over by this tree over there. I'm going to tie you up, so give me a chance to get away. So when she turned her back toward him, it made it easier for him now, because he didn't have to look in the eyes, to grab her by the neck and to strangle her. So that's why you have evidence of manual strangulation. But he didn't have the upper body strength to kill her. It takes a lot of strength in manual strangulation. So then he drags her over to this tree. And he has to kill her. So he picks up this rock and he drops it. And the ME, talking to them, how many times did he drop it? About three, four times. I come up with a profile of this individual here-- a white male, mid to late 20s. Okay, how do I come up with age? Because I start at 25, 25 years of age. That's usually kind of the mid-range when I start to see violent crimes. Based upon the level of sophistication of the crime, or the lack of sophistication in the crime, I'll start taking age away or I'll start increasing the age of the offender. ...

About the Instructor

Netflix’s “Mindhunter” was inspired by the FBI’s first criminal profiler, John Douglas. As chief of the National Center for the Analysis of Violent Crime, he conducted groundbreaking interviews with notorious criminals such as Charles Manson and Ed Kemper, changing interrogative tactics forever. On MasterClass, he teaches you to use his methods in everyday life, unlocking your intuition to read people's motives.

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John Douglas

Legendary Special Agent John Douglas teaches how criminal profiling methods can help you predict people’s motives to benefit your everyday life.

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