What You Need to Know

An important role in the prevention of crime and the apprehension of criminals is a police officer’s ability to inquire about an individual’s identity and the reason for the individual’s presence at an unusual time and/or place and/or under other suspicious circumstances. The quality and the frequency with which field interviews are conducted contribute materially to the success of an agency’s crime prevention efforts. Officers conducting field interviews must understand the legal basis and authority for these actions. By documenting interviews, members of an agency can contribute significantly to crime suppression and case analysis if the information obtained is properly recorded, collected and analyzed.

The Iowa City Police Department defines the field interview as “a brief detainment of an individual, whether on foot or in a vehicle, based on reasonable suspicion for the purposes of determining the individual’s identity and resolving the officer’s suspicions.”[1]

Officers always have the right of common law inquiry which in no way requires the subject to stop and/or answer any questions.  The physical detainment of an individual, either on foot or in a vehicle, is based on the existence of reasonable suspicion.  Reasonable suspicion is a legal standard of proof in United States law that is less than probable cause, the legal standard for arrests and warrants, but more than an “inchoate and particularized suspicion or ‘hunch.’[2]

The Iowa City Police Department’s definition of a field interview contains two primary justifications for the detainment: the first references the “resolving of the officer’s suspicions” and the second references “the purposes of determining the individual’s identity.”  Depending on what has been discovered during the investigation, resolving the officer’s suspicions could be the result of many bits of information that may or may not result in further action, such as an arrest or a release.  In recent years, however, determining the individual’s identity has made tremendous strides.   Data and technology have made determining one’s identity faster, easier and more accurate.  One can imagine what it would be like for an officer to find out later that the person that he or she detained is wanted for a serious crime in another jurisdiction. And, besides the guilt the officer may feel, the fact remains that a known offender is free and able to commit additional crimes.

By utilizing proprietary or public records in the field, an officer could formulate questions around a process known as “knowledge based authentication” to verify an identity during a detainment.   During a field interview, dynamic knowledge based authentication (broad based questions not previously arranged) is used to question a subject in areas that are predicated on information he or she should know.  This process is also sometime known as “out-of-wallet” questions.

An additional approach that is becoming more popular to positively identify subjects during field interviews is to leverage technology with data that links to personal attributes, such as a fingerprints or photographs.  This approach is known as biometrics.  Biometric identifiers are the distinctive, measurable characteristics used to label and describe individuals.[3]  Biometrics should be seen as a highly reliable form of authenticating one’s identity.   Field biometric tests can include fingerprint and iris scanning and facial recognition software.

The biometric with the most promising potential for field use is facial recognition.  Photographs are an already adopted piece of identifying information in the booking and recoding processes and therefore don’t require an agency to collect an additional data layer for biometric in-field testing.  Facial recognition software leverages these photographs and provides real-time verification of an individual’s identity, justify the arrest or enhance the line of questioning.

The first arrest booking photo or “mug shot” was taken by Allan Pinkerton, a famous US detective during the 19th Century.  Ever since that first photograph was taken by Pinkerton, police officers have relied on photos to be a part of the identification process.  Now, with highly reliable facial recognition technology, field interviews can be enhanced with the reliability and confidence of field application software.

At Vigilant, we are committed to bringing the latest technology solutions to our public safety partners.  We would love to hear from you if you and your agency are using biometrics in the field and how your agency is developing policies to adhere to the law, respect citizen’s rights and ensure a safe community.


[1] Iowa City Police Dept, General Order # 99-12, October 22, 2007
[2] Terry v Ohio, 392 U.S. 1, 27 (1968)
[3] Jain, A. Hong, L., & Pankanti, S. (2000) Biometric Identification, p.91-98