It would be hard to characterize O.J. Simpson’s public actions as normal.

From his run-ins with the law, to authoring a book called, "If I Did It," about a double murder for which he was acquitted, Simpson, at least on the surface, seems a little crazy.

But one psychologist, who has not treated Simpson, said the aging football star’s erratic behavior may have more to do with a belief that he is “invulnerable” to the law and criticism, than to a specific mental illness.

“His run-ins with the law have come to nothing,” said Stuart Fischoff, a professor of psychology at California State University, Los Angeles. “He's alleged and I've read where his fans believe his run-ins with the law are because he is being harassed by the law. Probably, he's come to believe he can talk his way out of anything (because) he has.”

Simpson’s latest brush with the law came this past Sunday when he was booked on charges connected with a robbery at a Las Vegas hotel. Click here to read more on the charges

Grasping at a Falling Star

Dr. Charles Figley, a Fulbright Fellow and professor of psychology at Florida State University, said Simpson's actions are that of a person eager to remain in the spotlight.

"It's the growing need of a star to maintain his level of fame — even infamy," he said. "(There's) a certain self-destructive and risk-taking behavior that may be associated not with personality, unless it's borderline, but with stress caused by lack of money ... or drug use, prescription or otherwise."

Fischoff said Simpson’s ego has been fed by his murder acquittal, a large fan base and the fact that his attorneys have largely protected his millions from the families of murder victims, Nicole Brown Simpson and Ronald Goldman, allowing Simpson to continue living a life of luxury.

“The book (“If I Did It”) was perhaps an expression of his feelings of invulnerability, some of which pre-dated the murders,” added Fischoff. “Does O.J. have a personality disorder? Probably. But his risky actions can also be a bizarre example of O.J. reality testing. Maybe he can get away with everything.”

Mental Illness?

Dr. Keith Ablow, Fox News contributor and psychiatrist, has not evaluated Simpson, but said that there are several things to take into consideration when looking at the situation in Vegas.

“You would wonder about personality disorder like narcissistic personality disorder, where the individual is unable to weigh their rights and needs in respect to other people,” said Ablow. “It makes it difficult for them to have genuine relationships because they cannot trust people."

Drugs and alcohol could have also played a part in Simpson’s action. “The other thing anyone would wonder is whether there were drugs or alcohol present at the scene of the crime," said Ablow. “What we do know is that for people who do have trouble, they don’t do well in the presence of alcohol and drugs."

Bipolar disorder could be another possibility, according to Ablow, citing elements of impulsivity in Simpson’s behavior.

“Everything is not what it seems,” he said. “You need to get to the real story. It’s not always that someone is a reprehensible individual. They usually lack certain critical resistance in the circuitry of their behavior. They don’t have a normal ability to reflect on whether what they are going to do is going to be responsible. Even if he doesn’t have mental illness, any decent therapist ... would say that he may have an underlying mental rage issue.”