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Private Investigator Basics Part 2: Interviewing

  • May 07, 2012
  • by Tom Shamshak

Core Competencies of Private Investigation Records ResearchEditor's note: This article was written by industry professional and guest contributor Tom Shamshak. The views and opinions in this article are that of the author and do not reflect the views of PInow. If you are interesting in becoming a guest contributor, send an email to [email protected]

Tom Shamshak is the Program Director and lead instructor for Boston University's Certificate in Professional Investigation, featured on PInow's Top 25 Investigator Training and Education Programs. He is a retired Police Chief and licensed private investigator with 33 years of investigative experience, and has been featured on CNN's Nancy Grace and ABC's 20/20. His company, Shamshak Investigations, services the Boston and Providence areas.

Private investigation is made up of three core competencies: records research, interviewing and surveillance. Many investigators consider interviewing the most valuable tool for gathering information. I firmly believe that about 75% of the total information gleaned during the investigation process comes from interviews.

Tom's Tips for Interviewing

Listen here for Tom's Tips for interviewing:

Tom's Tips for Interviewing by

What is interviewing?

Interviewing is the complex process of gathering facts from people that can then become testimonial evidence.

Types of investigations that require interviews
theft, situations involving the actions of an individual, missing persons, situations where an expert could be of assistance

Why do we conduct interviews?
Interviews are conducted to reconstruct a crime or event, to obtain evidence, to connect facts that seem disconnected, to look for leads, to identify facts and to find out what actually happened.

Who do we interview?
Plaintiffs, defendants, witnesses, victims, suspects, subjects of background investigations and experts.

Preparing for an interview

Preparation is the key to conducting a good interview. An investigative approach for interviewing begins with a prioritized list of witnesses to interview with the major witnesses at the top. A private investigator has to know as much as possible about the statement the witness has given to the authorities and has to know the facts of the case.

Researching the interview subject
Private investigators must conduct extensive records research and a background check on the interview subject before going to speak with them. Investigators should know basic background information about the witness, like if the witness is related to any of the participants in the event, if the witness wears glasses and if he or she has a criminal history.

Anticipating the interview subject’s needs
Depending on the nature of the case, interview subjects will have differing needs. In criminal defense cases people that are witnesses to crimes might fear retaliation or retribution if they step forward. They may fear going against the police. People that are friends or relatives of the crime victim are not going to want to talk to anyone from the defense. Private investigators have to be psychologically prepared for the difficulties of talking to these people and especially for talking to the crime victims themselves. They may be angry and private investigators have to calm them down and get them to share what they are going to say in court or at least to elaborate on what they told the police.

Documenting the interview
Notes should always be taken either during or immediately after an interview. Notes can be taken by hand, on an audio recording device or, if the interview subject is willing, on video. A private investigator must build rapport and make their interview subject feel comfortable enough to allow them to take notes. If the subject gives a very helpful statement that is exculpatory, a private investigator should ask to audio or video record the statement.

What should every investigator know about interviewing?

Setting up an interview
If possible, a private investigator should schedule an interview ahead of time with cooperating witnesses. If not, the investigator should make a cold call visit when the potential interview subject is most likely home. Depending on the circumstances, this could be the evening hours or weekend.

Engage in active listening
Private investigators should operate on the 80/20 rule. Interview subjects should be speaking 80% of the time and interviewers should be speaking 20% of the time. Active listening is an important aspect of interviewing as it encourages the flow of information as the interview subject is talking. Private investigators conducting interviews should confirm that they are listening by inserting “uh huh”s, “mmhmm”s, “I understand”s and “please continue”s into the conversation.  

Building rapport
Private investigators have to build rapport with interview subjects to earn their trust and get them to open up. This can be accomplished through participating in small talk upon entering someone’s home. Interviewers should look for some common ground with the interviewee and start a conversation on this subject. The key here is for the investigator to be able to establish an open communication channel, get some information and leave the door open for a follow-up interview.

Recognize truth vs. deception
Private investigators should begin interviews with closed questions and slowly shift to open questions which require some more thought. Interviewers should start off with basic questions about the subject’s background to which they already know the answers. While the interview subject is answering these questions, private investigators have to watch how they look while giving truthful answers. Later on, when the investigator gets to the meat of the questioning, he or she can recognize constant truthful behavior or a shift in behavior signified by vocal volume, pitch, halted speech, furtive facial gestures or micro-expressions.

Interpreting non-verbal communication
Focusing on these behaviors comes with experience. As a rule of interviewing, innocent people can be calmed down and guilty people get very nervous. They begin to display verbal cues discussed above. The interview subject that is guilty or that is lying will also display non-verbal cues like clenching fists, a reddening face, bulging veins and a loss of eye contact. 

After an Interview

Finalizing Notes
Private investigators must preserve their interviews by finalizing their notes or transcribing an audio or video recording so that it becomes part of the record. Investigators will then memorialize their notes in a report that includes when the interview occurred, how long it lasted, who was present and where it occurred. The report should describe what information was obtained. If it is an audio or video recording, then the information should be documented verbatim, and all notes should be kept until the matter is fully adjudicated as discoverable records.

Follow-up Interviews
Follow-up interviews are necessary in many different situations. If the witness did not give enough information initially, a private investigator would have to return to their home or place of work and continue building rapport until the witness was willing to speak truthfully. When information needs to be memorialized a private investigator should type up a narrative of the interview and conduct a follow-up. The interview subject should read the narrative, make corrections and sign off on the interview. If an investigator has found an inconsistency between the stories of two different interview subjects, it is a good idea to return to both of these subjects and conduct second interviews. If a private investigator needs further documentary evidence, such as telephone records, that were not available during the first interview, they should follow up with a subject and obtain these records.

New Leads
Interview subjects may give a private investigator information that leads to a new interview subject that was not initially included in the investigative plan. Whenever an investigator receives a new lead on a possible interview subject they should always follow up on the lead by conducting background research, contacting the new subject and scheduling and completing an interview. Private investigators should follow the same steps when preparing for, conducting and finalizing a follow-up interview as they would for the initial interview.

How can interviewing aid an investigation?

Interviewing is vital to many investigations because it gives a verbal confirmation of an event. In cases where a one time occurrence is being investigated, interview subjects are often the only people who saw what actually happened. This type of information is called testimonial evidence and can be invaluable in court, especially when combined with documentary evidence found during records research.


Each of the three core competencies of private investigation plays a critical role in working through an investigation. As a valuable tool, interviewing helps investigators get more information and a clearer picture of the situation they are investigating. Combining that knowledge with records research and the basics of surveillance helps investigators hone their skills and become more effective in the field.

Additional Parts of Private Investigator Basics Series

This article was written by an industry guest contributor. If you are interesting in being a guest contributor or have an article suggestion, please send an email to [email protected]

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