If a juvenile has had police contact more than five times before the age of 18, chances are high that they could become violent offenders in the future.

These are the offenders that Matthew DeLisi, associate professor of sociology and program coordinator of the criminal justice program, studied when writing “Delinquency in Society,” a new-edition textbook on juvenile delinquency. DeLisi collaborated with Robert Regoli, professor of sociology at the University of Colorado, and John Hewitt, professor of criminal justice at Grand Valley State University.

DeLisi also joined ISU sociology lecturer Peter Conis in co-editing another book titled “Violent Offenders,” which is due in stores this week.

DeLisi said contributions from academic fields outside of sociology and criminology have led to better research, which he discusses in his textbook.

“For a long time, criminology was just a subarea of sociology,” he said. “That has changed in the last few years. People from sociology have started reading outside of sociology and criminology. Every day we are learning more and more.”

DeLisi said one of the biggest advantages in the last 10 years in terms of learning about criminal behavior is the mapping of the human genome.

“We’ve learned about the brain and how it directly affects behavior. We can use this data to better understand crime,” DeLisi said.

Among other changes in studying criminology, DeLisi said instead of focusing on the age when juveniles commit crimes, sociologists are now learning to study people from birth to death. “Juvenile delinquency is a social problem. We study adolescence because that’s when juvenile delinquency occurs,” he said.

DeLisi said sociologists continue to wonder what happens to juvenile delinquents as they grow up.

“The life course is really big in criminology,” he said. “We’re interested in seeing how a criminal changes or stays the same over time.”

DeLisi said studying juveniles over their life course provides “a broader way to understand human behavior.”

“If you look at the people who are at the highest levels of crime, people who are the most criminal or most violent are going to be like that throughout their life,” DeLisi said.

While DeLisi’s studies have found that chronic juvenile offenders tend to continue crime later in life, Corp. Ken Kaufman with Ames Police doesn’t believe that’s necessarily true for juveniles in Ames.

Kaufman said there’s often a belief that juveniles who cause trouble will continue causing trouble into adulthood.

“I can name the bad guys, the juveniles, I have to deal with on a daily basis,” Kaufman said. “People believe that because these kids give us so much grief when they’re young that they will continue to give us grief when they are old. That’s just not true.”

DeLisi also said a number of factors contribute to a young person becoming involved in crime including: family situation, socioeconomic status and abuse.

“It’s always both nature and nurture. They really mutually enforce each other,” he said.

However, DeLisi said if a child has the special gene MAOA, which encourages deviant behavior, but if the child has a good family background it is unlikely that he or she will become a chronic offender.

Kaufman said even though there isn’t a “true correlation between young and old,” there also is not a true correlation with socioeconomic status and juvenile crime.

“Everyone wants to point the finger at socioeconomic status,” he said. “It’s more of a nurturing situation.”

Kaufman said in many cases, children growing up in crushing poverty are not the troublemakers.

Often times, if the children do not have a family mentor to look up to, they tend to start trouble.

“I’ve seen rotten kids from affluent homes,” Kaufman said.

Kaufman said the most common type of juvenile crime was crime against property, rather than crime against people. The most common types are “burglary theft, and issues with kids stealing from each other in school.”