Forensic psycholinguistics: The study of psychology and language in criminal justice. Was the kidnapper a man or woman? A friend of the family or a stranger? Well-educated or not?

How about a threat against a business or an official? Should it be taken seriously? How likely is it the suspect will act? These are some of the questions forensic psycholinguists try to answer. "Words of Conviction" is an FBI thriller based on this science.

Sharon S. Smith, PhD., a forensic psycholinguist and retired FBI Agent, graciously agreed to share her knowledge with me as I worked on "Words of Conviction." Her 25 years in law enforcement, which included time in the field and at the elite Behavioral Science Unit at the FBI Academy, provided just the background I needed to create my protagonist, Agent Mackenzie Graham, and weave a story about her.

Recently, Sharon and I sat down in her kitchen and spoke with her about her career. I began at the beginning: What is forensic psycholinguistics?

"Language reveals not only what we say we are thinking," she told me, "but also underlying thoughts that we may not want to reveal publicly." Words can reveal personality characteristics (including depression, anxiety, impulsivity, and paranoia) as well as unmask current and possibly future behavior. "What's fascinating to me," Sharon said, "is what we can learn about other people beyond what they are saying" based on their language.

A forensic psycholinguist puts that knowledge to work in the criminal investigative arena. For example, he might assess the probability a threat will be carried out, or, detect deception in an interview situation. In the case of "Words of Conviction," the forensic psycholinguist was called upon not only to analyze a kidnapper's note, but see if she could discern his identity from his Internet blog posts.

Sharon didn't grow up longing to be a forensic psycholinguist. In fact, she began her working life as an elementary school teacher. After five years, she discovered her real passion was teaching adults and began earning advanced degrees so she could teach at a university level. In a doctoral statistics class, she met two FBI agents who gave her the idea of applying her psycholinguistics training to law enforcement. And that's how Sharon went from parsing words to kicking doors.

Psycholinguists study the psychological basis behind the language people use. As an FBI agent, Sharon could immediately see the application of this field to law enforcement. "Law enforcement at whatever level has to talk to people," she told me. "That's how we get information." Every poker player knows about "tells"--those non-verbal clues to the strength of your hand. But Sharon says that "research indicates that the language indicators are more reliable than non-verbal clues" in revealing the truth.

For example, when questioned by law enforcement, a person may "back away from the truth" by using qualifiers: "Yes, I was sort of angry with my girlfriend." Other qualifiers like "kind of", "possibly", and "I believe" may indicate the need to press the interview further. Protest statements ("How dare you accuse me of hurting her!") in response to direct questions ("Did you hit your wife?") may also indicate deception. And spontaneous negations ("Were you in Fredericksburg yesterday?" "No!") are clues as well.

"Words of Conviction" deals with a kidnapping, and Sharon was my go-to source for the linguistic clues in the story. In my next post, I'll explain how a kidnapper's words may well provide crucial indicators of his (or her) identity.