According to one historian, the anti-government rallies that made their way across the country last summer, known as tea parties, may explain more about Americans than their views on high taxes and gun control.Ohio State University historian Randolph Roth claims that the distrust of government on display at the tea parties earlier this year has appeared sporadically throughout America's history and may be linked to homicide rates. In short, when Americans begin routinely complaining about how they hate their government and don't trust their leaders, they commit more murders.Although odd suspects, Roth believes that people's views about the legitimacy of government and how much they identify with their fellow citizens play a major role in how often they kill each other – much more so than the usual theories revolving around guns, poverty, drugs, race, or a permissive justice system."The predisposition to murder is rooted in feelings and beliefs people have toward government and their fellow citizens. It is these factors, which may seem impossibly remote from murder, that hold the key to understanding why the United States is so homicidal today."

If you look at the evidence over time, poverty and unemployment don't lead to higher murder rates, as many liberals argue, he said. But locking up criminals, using the death penalty, and adding more police don't hold the murder rate down either, as conservatives claim.

At any one point in time, researchers may find an association between one of these causes and homicide rates in a particular area. But once you try to apply those theories more broadly, at different places and in different eras, the links disappear.

For example, during the Great Depression the homicide rate in the United States went down, even while poverty was increasing. In the 1960s, the United States had more police and more people in prison than nearly any other nation on earth, along with strong economic growth – and yet the murder rate skyrocketed.

"Criminologists make a case for one theory or another by going through records for a short period of time. But if they try the same theory in colonial America or the early 20th century, it won't fit. That's where it helps to have a historical perspective," Roth said.

In his analysis, Roth found four factors that relate to the homicide rate in parts of the United States and western Europe throughout the past four centuries: the belief that one's government is stable and its justice and legal systems are unbiased and effective; a feeling of trust in government officials and a belief in their legitimacy; a sense of patriotism and solidarity with fellow citizens; and a belief that one's position is society is satisfactory and that one can command respect without resorting to violence.

When those feelings and beliefs are strong, homicide rates are generally low, regardless of the time or place, Roth said. But when people are unsure about their government leaders, don't feel connected to the rest of society, and feel they don't have opportunity to command respect in the community, homicide rates go up.

While measuring trust in government and fellow citizens provides one challenge for historians, the other is figuring out homicide rates before the advent of national crime statistics.

To do this, Roth created the Historical Violence Database, housed at Ohio State, which allows researchers to examine data from many studies of homicides from a variety of time periods and places. This database now includes information on tens of thousands of homicides in different areas of the United States and western Europe from medieval times to the present.

The database includes detailed studies of homicides in places as different as New York City, Holmes County, Ohio, and regions in the far West and Deep South.

The lesson to take away from his research, Roth said, is that the best way to reduce homicide rates has nothing to do with guns, or police, or courts or even economics.

"Political leadership has the greatest opportunity to have a real impact on homicide rates," he said. "It is difficult, I know, but we need a leader who can unite the country around some values and beliefs that we can all accept. That said, leadership can be effective only if the conflicts within a society are manageable. When they become unmanageable, as they did during the Civil War, even a great leader like Abraham Lincoln can't pull the nation together and keep homicide in check."