The idea that Heath Ledger was possessed by a demon during the production of The Dark Knight is not new. Some folks truly believe that the young actor opened himself up, and became susceptible to, a truly evil force. One that drove Heath's performance as The Joker.

One of those people that believe Heath Ledger may have been under the influence of Satan's minions in his portrayal of this iconic Batman villain is The Reverend Bob Larson, the world's leading exorcist, and foremost expert on cults, the occult, and supernatural phenomena. He is currently making the rounds in discussing the authentic nature of the exorcisms seen in The Devil Inside.

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We recently caught up with Bob to chat about this new thriller. Along the way, we began discussing the dangers of demon possession in acting. And how certain roles or performances may make a person more accessible to demons. Heath Ledger's name came up automatically while discussing this topic. Which begs the question: If Heath Ledger was possessed by a demon...Did that demon want to act? Because if that is a demon, he is giving one heck of a performance. And he is quite cooperative with the crew. Why would a demon possess an actor, and then continue to carry through with making a movie. A movie is hard work.

In my professional opinion, I don't think a demon has the patience for all the wait time that occurs on a set. I could be wrong. Maybe this particular demon wanted to give the performance of a life time. I imagine him shuffling through Hell with his hat and cane right now, screaming, "See, that Oscar is mine!"

Here's what Bob had to say on the matter.

Like The Devil Inside, the more recent exorcism movies have been these faux-documentary, found-footage type thrillers. The actors are never well known. When we are watching this movie, and we see these people who are possessed on screen, acting out this demonic reckoning, and they get lost in what is a very scary, very real performance...Does that make them more susceptible to actually being possessed by a real demon? Are they opening themselves up in an unhealthy way? Especially when these actors are not on a contained movie set. But, like we see here, they are in a real location for the purpose of authenticity in the making of the film?

Bob Larson: Well...I'd be more worried about a Heath Ledger and a Joker character. We all know where that ended up. As legend has it, even Jack Nicholson warned him not to do that movie, because of the nature of that role. There is always a danger in loosing that line of distinction. But I don't see that happening in this particular film. Because I think they take a realistic, factual approach to it. At the beginning of the film, which I like, there is a lot of interaction and discussion about what exorcism is. How it operates. Through the dialogue, the questions of these young seminarians that are in this exorcism school give very authentic answers. There was very little that I could disagree with there. At least there is the semblance of factuality here, which is very strong...Which is very different from something like Paranormal Activity, which is just about looking for things that go bump in the night.

Let's go back to Heath Ledger. Its your professional opinion, as the world's most renown exorcist, that Heath Ledger was, in fact, possessed by a demon during the making of The Dark Knight. That's what propelled his performance as The Joker...

Bob Larson: I would say...something overtook that man. There is a strong possibility that somehow, he just took on too much of the evil of this character. After all, whether it was psychological or spiritual, he could not draw that distinction anymore. That is not the first time I've had an actor tell that sort of thing to me. When they are called onto portray that role. With this movie here, though, I don't see that happening.

Have you actually had professional actors come to you after portraying a certain character? Or something that is evil in a film? Do you find actors coming to you for character exorcisms?

Bob Larson: I have. There have been instances of that. Obviously, I deal with political figures, business people, as well as ordinary people...A lot of people in the entertainment industry. But I am sworn to secrecy on that. Clergy confidentiality doesn't allow me to discuss anything about that. But...There is that danger. I wouldn't say that it is a common danger. But it certainly is at work out there.

We know that demons are very smart, and very cunning. Basically, what you are telling me is, demons know, and are more apt to stay away from something like The Devil Inside. Because that is cliché. They are more apt to go where they won't be detected...

Bob Larson: I think that is fairly accurate. However, with what they are portraying in this film...The caution is..."Do not try this at home." Know what you are doing. When we train people to go through exorcisms, they go through an extended apprenticeship program. Hours of training. Hours of sitting alongside others who are performing exorcisms...Before they ever step out on their own. To take this on single-handedly, so to speak. There is always danger there. There is physical danger. There is the danger of physical violence. There is the danger of harm to the other person. I have been through some pretty scary situations in the years that I have been doing this. Its something you approach with a great deal of caution. What I do like about this movie is that they are interested in the scientific aspect of it. Can you psycho-neurologically determine and identify possession. In fact, I think you can.

Which brings up my next question. Here we have actors in a movie, who are believable on screen as a person who has been possessed. If we put that same performer in front of you, will you be able to tell the difference between someone who is acting the part of a soul possessed and someone who is actually soul possessed?

Bob Larson: Look, there are no special effects in a real exorcism. Whatever is happening, is really happening. If the eyes are dilating, they are really dilating. If the body is contorting in a way that is seemingly impossible for a person, from a muscular skeletal manner, to do...It is really happening. There are no smoke and mirrors in an actual exorcism. This is for real.

So there is no way an actor could fool you?

Bob Larson: I would know in a short period of time. I've had people try to fool me. For sick reasons, or just for curiosity, to see if they could. First of all, I am not going to do this in most cases unless I have profiled the person's history, and I have checked into their background. We don't take random people off the streets. And say, "Oh, we're going to do an exorcism." There is some factuality there. Secondly, you spend a fair amount of time on an exorcism. You don't just jump in, throwing around a bunch of holy water. And waving a cross. You ask a lot of questions. Anyone who is pretending wouldn't get very far, after a couple of hours of questioning.

To read more of our conversation with Bob Larson:, where we talk about animal possession and the dangers of the entertainment business: CLICK HERE