Bellefonte, Pennsylvania (CNN) -- Former Penn State assistant football coach Jerry Sandusky, on trial on child rape charges, is expected to be examined Sunday by a prosecution psychologist, according to a source with knowledge of the case.
The examination is the result of a court order Friday allowing the defense to introduce testimony on whether Sandusky suffers from a disorder.
The development is not expected to delay the trial, which is scheduled to resume Monday.
The defense is expected to begin presenting their client's case this week after the prosecution rests.
In a motion, Sandusky's lawyers said the content of letters written by Sandusky to alleged victims may be a result of histrionic personality disorder, rather than the prosecution's contention that the letters were part of "grooming techniques" commonly employed by sexual predators.
The defense said it intends to offer expert testimony from a psychologist who "will explain that the words, tones, requests and statements made in the letters are consistent with a person who suffers from a histrionic personality disorder."
According to the National Institutes of Health, those with histrionic personality disorder "act in a very emotional and dramatic way that draws attention to themselves."
"The goal of a person suffering from this disorder in writing those letters would not necessarily be to groom or sexually consummate a relationship in a criminal manner, but rather to satisfy the needs of a psyche belabored by the needs of such a disorder," the defense lawyers wrote in their motion.
Judge John Cleland issued an order on Friday granting the defense motion, under one condition: that Sandusky "make himself available to (prosecutors) for the purpose of preparing rebuttal psychological/psychiatric testimony."
Sandusky remains free on bail and under house arrest during his trial.
The longtime Nittany Lions defensive coordinator faces 52 counts tied to what prosecutors say was his abuse of at least 10 boys over a span of 15 years. The state says Sandusky met many of his alleged victims through Second Mile, a charity for underprivileged youths that he founded.
Now 68, Sandusky pleaded not guilty and has maintained that his contact with children was not sexual.