What is the insanity defense? Are some people's brains so different from yours that it makes sense to categorize them differently under the legal system? How could a mother kill her children? Can you commit a crime without meaning to?

How does a legal system decide how to rule on these issues?

And how are science and law strange bedfellows?

Welcome to the inner cosmos with me, David Eagleman.

I'm a neuroscientist and author at Stanford.

And in these episodes, we sail deeply into our three-pound universe to understand why and how our lives look the way we do.

Thank you. look the way we do. Now, we all hear the word insane.

Somebody's acting insane, something like that.

But the first thing to note is that insanity is not a medical term.

It's not used in psychiatry or neuroscience. It's instead a

term used by the legal system. And I'm going to do a two-part episode about the insanity defense,

where it comes from, and why it is so difficult as a society to decide where we want to draw our lines in the

sand. What I mean is sometimes a person commits a crime and we say they're clearly different from us,

but we're not sure quite how, and we're not sure if that should release them from culpability.

As we're going to see, there is no hard and fast line where we as a society can say, oh, that person is on this

side of the line and this person isn't. Now, this is a theme I've expressed in various ways in all

of these episodes, which is that brains are very different from one

another. And most everything that we are interested in lives on a spectrum and more than a

spectrum on a very complicated landscape. People are very different on the inside. And the question

is, how do we build rules as a society to make things run

well? So let's get started. What I want to tell you about is a young woman named Andrea. So by the time

Andrea was a teenager, she held the world by the tail. She was the valedictorian of her high school. She was the captain of her

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