Interviewing suspects is a crucial tool for police forces and the prosecution. Sometimes it's the only investigative avenue available to law enforcement personnel faced with solving a case in which forensic evidence is lacking, no longer exists or has been destroyed.
According to Justice Edson Haines of the Ontario Supreme Court in 1972, such cases are not uncommon: "In many circumstances, physical clues are entirely absent. The only approach to a possible solution is the interrogation of the suspect and others who may possess useful information."
Field research corroborates Justice Haines' statement. In 1980, researchers reported that forensic evidence was either unavailable or not important in 95 per cent of cases in England, while other researchers concluded in 1996 that forensic clues were gathered in only 10 per cent of offences investigated by police in the United States.
In light of the importance of potential evidence resulting from a police interview, and from a personnel selection standpoint, identifying the characteristics of competent and suitable interviewers can only benefit the general interview performance of investigative units, the crime solving rates of police services and the public's trust.
The idea behind this research was to identify the profile of a person best suited to conduct police interviews. Three measures were used to develop this profile: a personality inventory, a competency measuring tool and a communicative suspiciousness questionnaire.
The personality inventory measured five broad domain traits:
- Openness. This trait refers to the creativity and artistic sensitivity aspects of an individual. High scorers tend to be original and unconventional, while low scorers are plain and uncomplicated.
- Conscientiousness. This characteristic points to industriousness and devotion. Persons with high scores are attentive and hard-working, and those with low scores are neglectful and lazy.
- Extraversion-introversion spectrum. This trait depicts characteristics along an external reality versus inner feelings axis. It corresponds to those who are open and exuberant at one end of the spectrum, and those who are reserved and timid at the other end.
- Agreeableness. This element features concepts of humanity and compassion. Persons at the high end are inclined to be obliging and genuine, and others at the low end are contentious and harmful.
- Neuroticism. This factor represents the emotional stability of an individual. High scorers are distraught and tormented, and low scorers are calm and tranquil.
The competency instrument measured five dimensions:
- Careful-tenacious. Individuals who are methodical, attentive to detail and able to carry on a constant effort.
- Controlled-non-reactive. An individual's ability to withstand pressure and the corresponding non-reactivity towards stressful situations.
- Dominant-insisting. A coercive style where the interviewer presses the interviewee for answers.
- Communicative. The characteristics associated with good interpersonal and communication skills.
- Benevolent. The kind-hearted attributes of an individual.
Lastly, the suspiciousness tool evaluated the suspicion level of a sample of police interviewers. An overly suspicious interrogator might misinterpret a suspect's inoffensive statement for an attempt at deception, which might lead him or her to aggressively pursue a line of questioning down a path to nowhere. On the other hand, a dupable interviewer could easily accept a suspect's alibi or version of events and discontinue a meticulous examination of all the facts at the risk of overlooking crucial evidence.
An invitation was sent to the chiefs of 22 major police departments in Canada. A total of 47 serving police officers (40 men, seven women) from across Canada who were in a position of conducting interviews of suspects involved in major crimes, responded and completed all three questionnaires.
The second portion of the research asked the participants to classify, over a six-month period, the conclusion of their interviews in any of four possible outcomes: the suspect denied any allegation, the suspect admitted to some incriminating facts, the suspect confessed, or the interviewer cleared the suspect as innocent. A fifth possible outcome, the suspect remained silent throughout the interview, was not retained for the purposes of this research. The police participants collected data from 162 interviews.
The data generated from these participants and interviews was put through a series of statistical analyses and provided the basis for the following conclusions.
Other than being the first of its kind, this research led to some notable findings.
First, the competency instrument, which was initially developed on a population of Dutch police officers and later validated on a similar sample in Belgium, was also shown to be applicable to a Canadian population across cultural and linguistic lines.
Second, the results obtained from the personality inventory with a Canadian sample were in line with other European researchers, indicating its reliability.
Third, the communicative suspiciousness tool had never been related to the other two measuring instruments before. The findings showed that the level of suspiciousness was negatively related to the communication competency and the conscientiousness and extraversion personality dimensions. In other words, the greater the level of communicative suspicion on the interviewer's part, the less conscientious and extroverted he or she turned out to be. Both dimensions play an important role in several interviewing skills. This combination may be an unfavourable profile for interviewers wishing to establish a rapport with interviewees.
Overall, in the current sample, the more suspicious interviewers appeared to be, the less competent they were in their communicative skill set, and perhaps not as conscientious in attending to appropriate cues. Negligent and disorganized interviewers with poor communication skills are more likely to interpret communication messages as generally suspicious and label them deceptive.
Fourth, those scoring high in the careful-tenacious dimensions were also more conscientious and less emotionally volatile. In terms of interviewing ability, these individuals would represent some of the best candidates. These individuals are methodical, attentive to detail, industrious and composed.
Fifth, in terms of the controlled-non-reactive competency dimension and the personality traits of conscientiousness, agreeableness and neuroticism, this combination of characteristics also represents a desirable interview profile for a police investigator. High scorers in this competency would be able to withstand pressure in dealing with difficult interviewees, be more perseverant, reliable, patient, cordial and even-tempered.
Establishing and maintaining a positive rapport is a central component to a successful interview. An ideal personality and competency profile of a police interviewer may not exist yet, but police agencies could be mindful of the developing research in the selection of their personnel in investigative units. Further replications are warranted before stronger conclusions can be reached and recommendations made.
Nonetheless, the data obtained from the interrogation outcomes permits some tentative conclusions. A statistical analysis revealed that 24 per cent of the variability in the outcome of the 162 interviews collected was accounted for by certain personality traits, competency characteristics and degrees of suspiciousness.
A statistical analysis revealed that 24 per cent of the variance in the outcome of an interview was accounted for by two of an interviewer's personality traits — conscientiousness and extroversion — as well as his or her degree of suspiciousness, and how careful and tenacious he or she was during the interview.
This means that 24 per cent of an interview outcome can be attributed to certain personality traits and competency characteristics, while the remaining value (76 per cent) can be explained by other factors such as the profile of the suspect, peculiarities or different aspects of the crime itself, the quality and quantity of the evidence, and measurement error.
Considering that nearly a quarter of what transpires during an interview is associated with the profile of an interviewer, it would be important to select the right person for the right kind of interview, taking into account the suspect and the crime.
This experiment is only the beginning of what will hopefully evolve into a matrix where the profile of a police interviewer can be matched to that of a suspect. Many more experiments of this type will need to be conducted to accumulate enough data before this matrix becomes a useful tool in finding the most efficient match between interviewer and suspect.
Funicelli, M., and Laurence, J.R. (2017). Personality Factors, Interview Competencies and Communicative Suspiciousness of Canadian Police Interrogators of Criminal Suspects. Investigative Interviewing: Research and Practice. Vol 8(1), pp. 1-15.