AMES, Iowa - It is not uncommon for investigators to interview people who have been tired and had very little sleep during a criminal investigation. Although it is not always possible, an Iowa State University study has found that sleep disruptions or deprivation can limit the information available during interviews.
This study, published in the academic journal SLEEP is the first to examine how sleep affects interview behavior or interrogations. Zlatan Krizan is an ISU psychology professor. He says that while there have been beliefs for decades about the effects of sleep on interrogation subjects, he and his co-authors, Christian Meissner, and Anthony Miller, found no direct scientific evidence to support this belief. Krizan believes the results of their study will have implications for suspect interviews and the many interviews that investigators conduct with victims or witnesses to crimes.
Krizan stated, "This is the first evidence that really hits on the efficacy sleep loss as an approach to elicit further information."
The research team conducted interviews with well-rested and sleep-restricted individuals to compare their answers regarding past criminal activity. Results show that sleep-restricted subjects provided 7 percent less information about the crime in terms of who and what, when, why.
Krizan stated, "Think about how many interviews are conducted and what information is collected during a homicide investigation." "In the case of investigators interviewing people who are sleep-deprived, they are missing five pieces critical information they could use to cross check or corroborate other information."
Although they were not statistically significant, findings related to the quality and precision of information revealed a similar pattern. Additional findings indicated that sleep deprivation could have a negative impact on motivation, making it harder to recall details.
Common sleep loss
Researchers cited anecdotal accounts of investigators awakening suspects to conduct interviews. Krizan said that it is not uncommon for victims, suspects or witnesses to feel tired or to function on only a few hours sleep due the circumstances of most crimes.
Researchers randomly assigned the 143 interview subjects to either a sleep-restricted group or a control group in order to reflect these interview conditions. The sleep-restricted participants were told to go to sleep two hours earlier than usual and to wake up two hours earlier in order to get up eight hours sleep over the course of two days. Participants wore watches to monitor their sleep patterns and track their compliance.
Participants were asked about their criminal history based upon a list that included 20 crimes. These ranged from shoplifting and transporting fireworks to driving under the influence. The most serious crime was underage drinking, experimentation with illegal drugs, and driving under the influences.
Professor of Psychology, Meissner says more research is required to understand how sleep loss affects behavior.
Meissner stated that people who slept less were not as motivated to recall data or felt it required more effort. These patterns indicate that sleep loss and increased fatigue may play a role in disclosure.
Researchers acknowledged that participants in the study did not face any legal consequences as would a suspect in a criminal case. They likely felt guilt or shame similar to other suspects, victims, or witnesses in a crime. This is an area that researchers plan to further explore in future research.
Federal Bureau of Investigation granted funding for the research.