On Monday, the defense team for Jerry Sandusky filed a motion to have a psychologist to testify about "histrionic personality disorder," a condition which the defense will argue Sandusky suffers from. In response to the "love letters" Victim No. 4 said he received from Sandusky, the defense will argue that the letters match up with the behavior of someone with histrionic personality disorder.

The condition normally begins in early adulthood. The symptoms are often over-the-top behavior, extra-theatrical emotion, and other kinds of attention-seeking behavior.

It is not an easy condition to diagnose, according to Dr. Carol Bernstein, an associate professor of psychology at New York University. As Bernstein told ABC News:

If someone exhibits sexually inappropriate behavior and that's all they have out of the several characteristics, that's not a personality disorder. Any sexual predator exhibits sexually inappropriate behavior.

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