At the trial this week of Raulie Casteel, the Michigan man accused of going on a shooting spree in October 2012, Casteel's lawyer explained that his client shot at nearly two dozen people because of his conspiracy beliefs.

"Casteel thought drivers along Michigan's Interstate 96 were part of a government conspiracy against him," he said in court Monday, according to ABC News. So he started firing.

Casteel, a husband and father, is taking the stand in his own trial, which continues Tuesday.

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"To my way of thinking at the time, [the shooting] was to get rid of the demons so to speak. It was those thoughts — the fear, the anxiety," the confessed shooter said Monday.

After being fired from his job as a scientist, Casteel says he believed his phone calls were being monitored and that government helicopters were watching him.

Casteel is only one of many violent conspiracy theorists who have taken up arms and attacked innocent victims.

In 2002, Luke Helder, a Minnesota college student, left 18 pipe bombs left in mailboxes that injured six people in Iowa, Illinois, Nebraska, Colorado and Texas. Before the bombings Helder wrote a six-page letter to a university student newspaper discussing his belief in various conspiracy theories. Helder wrote that each person can create his or her own reality, and that "once you begin to realize the potential you have as a consciousness/soul/spirit, you will begin to harness the abilities you have to produce realities."

Helder stated that his bombs were designed as "attention getters" that would allow him to tell the world about his conspiracy beliefs: "I'm doing this because I care…In the end you will know I was telling you the truth anyway."

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Jared Loughner, the gunman who killed six people and injured 14 others including Rep. Gabrielle Giffords in a 2011 Tucson shooting, also advocated conspiracy theories. According to a profile in The New York Times, Loughner "became intrigued by anti-government conspiracy theories, including that the Sept. 11 attacks were perpetrated by the government and that the country’s central banking system was enslaving its citizens."

In addition to his beliefs associated with a co-called "New World Order," he was also convinced that many NASA programs were fake and that images of the Mars surface taken by the Mars Rover were hoaxed as part of a government conspiracy.

Aaron Alexis, a government contractor who killed a dozen people and injured eight others at the Washington Navy Yard in September 2013 told police that he had been harassed through a government mind control program using ultra low frequency microwaves. In one document Alexis wrote: "An ultra low frequency attack is what I’ve been subject to for the last three months, and to be perfectly honest, that is what has driven me to this."

Needless to say, there is no evidence that the U.S. government can control anyone’s thoughts or decisions using microwaves, though that claim is common in conspiracy theory literature.

Conspiracy Theories, Mental Illness, and Violence

Part of the reason that conspiracy theories are so popular is that we are hard-wired to find them. Our brains, even without the help of books, late-night talk shows, and web sites promoting all manner of conspiracy theories, have a tendency to generate conspiracy-type thinking. The human brain sometimes has a difficult time understanding why things happen, and two unrelated events can appear to be connected in some way.

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Seeing hidden connections and causes is a key element of conspiracy thinking. But that logic is a common fallacy with a Latin name: post hoc ergo propter hoc (Latin for "after this, therefore because of it"). Because the human mind seeks connections, people often mis-attribute causes, thinking that "B happened after A did, so A must have caused B." It makes sense, and it’s often true, but not always. It’s like saying "roosters crow before the sun rises, so the roosters must have made the sun rise."

Taken in extreme, this type of thinking can result in clinical paranoia. The "Statistical Manual of Mental Disorders," the so-called bible of psychiatry, notes that in paranoid disorders "The persecutory delusions may be simple or elaborate and usually involve a single theme or series of connected themes, such as being conspired against, cheated, spied upon, followed, poisoned or drugged, maliciously maligned, harassed, or obstructed in the pursuit of long-term goals. Small slights may be exaggerated and become the focus of a delusional system…. Common associated features include resentment and anger, which may lead to violence."

Paranoia and conspiracy thinking lead to feelings of powerlessness or helplessness. Those who believe in conspiracies often see themselves and those around them as victims, pawns in some sinister master plot. They often feel intellectually superior to others around them, especially the "sheeple," a pejorative term for the unenlightened masses who are routinely deceived by government lies and misinformation.

Yet even armed with that conspiracy "knowledge" they cannot attack their oppressors directly. They cannot take out their anger and frustration against a faceless conspiracy — there is no official New World Order or Illuminati spokesman or headquarters to attack — so as a result the anger is released on symbols of the government (such as elected officials) or random crowds.

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Extreme acts of violence can seem to be a logical reaction to conspiracy beliefs. If one sincerely believes that President Obama is the Antichrist who at any moment will take away American's guns and trigger Armageddon, or that elected officials in the G.W. Bush administration murdered nearly 3,000 innocent citizens in a Sept. 11, 2001, conspiracy, then resorting to violence may seem reasonable and appropriate. This is especially true when conspiracy theories appeal to political extremists who already harbor a distrust of the government and a willingness to take up arms.

Of course it is important to remember that most violent people are not conspiracy theorists, most mentally people are not violent, and that most conspiracy believers are not violent.

Though conspiracy beliefs do not cause violence, they can give a name and form to generalized rage and helplessness and set the stage for violent actions.

Photo: Credit: Raulie Wayne Casteel is shown in a booking mug. Credit: Livingston County Sheriff.