Jerry Sandusky's defense team filed a motion Monday that asked permission for a psychologist to testify about histrionic personality disorder, a psychiatric disorder characterized by dramatic, emotional and attention-seeking behavior.

The former Penn State assistant football coach is charged with 52 criminal counts of sexual abuse involving 10 boys over a 15-year period. The motion was intended to discount the prosecution's argument that letters from Sandusky to the boys were not "grooming behavior" to lure them into an inappropriate sexual relationship.

The first witness in the trial, known as Victim No. 4, said the former coach sexually abused him and sent him "creepy love letters." The defense said a psychologist will explain that the "words, tones, requests and statements" made in the letter are consistent with a person who suffers from a histrionic personality disorder, according to the motion.

The Diagnostic and Statistical Manual of Mental Disorders, or DSM, defines people with the personality disorder as having an excessive need for approval and exhibit inappropriate seductive behavior. The condition usually begins in early adulthood, and people with the condition are usually dramatic, energetic and flirtatious. "Histrionic" is a term meaning "dramatic or theatrical."

According to Cleveland Clinic, people with the disorder usually have good social skills, but they tend to use those skills to manipulate others to make themselves the center of attention.

Patients must not only undergo a full psychiatric evaluation to be diagnosed with the condition, but psychiatrists must also have an understanding of how they operated over an extended period of time in multiple areas of their lives, including work, love, relaxation and play, said Dr. Carol Bernstein, associate professor of psychiatry at NYU Langone Medical Center, who is not involved with the Sandusky trial.

People with the disorder must exhibit at least five characteristics of the disorder, some of which include: being uncomfortable when they are not the center of attention, rapid changes in emotions, being overly concerned with physical appearance, constantly seeking reassurance and approval and exhibiting inappropriate seductive or flirtatious behavior.

The condition can be difficult to diagnose because parts of anyone's character and style can make one behave in a certain way in certain situations, said Bernstein. But even if people are diagnosed with a disorder, it does not justify inappropriate behavior and does not make them insane.

"These disorders can indeed be real, and sometimes they can be pathological, but you have to look at the context from where they occur," said Bernstein.

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

Even with a diagnosis though, Elyn Saks, associate dean and professor of law, psychology, and psychiatry and the behavioral sciences at University of Southern California Gould Law School, said the legal argument would be a "stretch."

"Typically, for an insanity argument, a person must be out of touch with reality at the time of the crime," said Saks. "It is very strict. While personality disorders can have transient psychotic symptoms, this would be a stretch as a viable argument."