By Dave Thompson, CFI

Biases are rampant in all industries, but not many have the disastrous impact that those in the criminal justice or employee relations field may experience.  The destruction of morale, wrongful termination or conviction, and the potential of continued wrongdoing by the guilty party can all result from a biased investigation or interview.

There are too many types of biases to list concisely, and it seems that multiple research papers have categorized them in their own way.  For the sake of sanity, I’ve created my own list from what I  believe are some of the most prevalent biases in the investigative world.

Unlike the more academic labels and titles, such as “confirmation bias”, the below list is slightly more informal and may be the best one you will ever read, but don’t believe me without reading it, because I am, in fact, biased.


  • DIY EffectI did the work, so it must be right, and I’ll defend it relentlessly.  Don’t mind the bruised thumbs, cut on my face and sore back – that’s part of the job – and it’s also why I refuse to take your post-project suggestions.

I once stared at a sidewalk for about four hours because I laid the foundation and designed it myself.  Often, when we put all the work into something, we tend to overvalue its accuracy and ignore the opinions of others who come in after-the-fact.  If you led an investigation, put hours, weeks or months into it, the best thing you can do is have a second set of impartial eyes review your work.  It may be unnerving, but it will result in a more complete and accurate result.

  • Frequent Flier BiasHere we go again, this guy may as well have loyalty points for how many times we have had to investigate him – can somebody get him an upgrade?

Whether it’s the same “suspect” for multiple issues, a consistent complainant or the “local weird guy” – none of these predisposed opinions should impact the integrity of the current investigation.  Slow down, look at the evidence independent of the reputation and let it guide the investigation where it may.

  • Pants on Fire, Must be a LiarHe scratched his face, coughed a few times and picked some lint off of his right knee.  Got ‘em!

This topic has been covered ad nauseum, but is still highly prevalent in investigative interviews or any form of communication, really.   There is countless research debunking the idea that we can identify deception purely by these physical cues, and here is a great example of a recent publication stating just that – The Analysis of Non-Verbal Communication.  Understanding that anxiety can be caused by a myriad of situations is important for the interviewer to recognize, and they should explore those areas of concern to determine the root cause.

  • Hand in the Cookie Jar Well, we’ve got the evidence this time.  It’s not like forensics could be wrong, I mean take hair analysis for example… Oh, wait.

Challenge your evidence, it could be wrong.  Check out this information from the Center for Integrity in Forensic Sciences.

Everything from accounting reports to forensic evidence has variables, exceptions, and percentages of error.  Before you start making accusations, investigate your evidence and challenge its accuracy.  Probably shouldn’t lie about it being in your possession either, but that’s for another article.

  • Eyewitness WoesI can’t remember what I had for dinner last night, but I know for sure the guy was 5’11, medium build, blue eyes and had a solid beard… at least, I think he did.

One of the many causes of wrongful convictions is eyewitness misidentification.  This can be seen in every investigation ranging from homicide to theft to sexual harassment.  Relying on the observations of imperfect memories can be disastrous.  Eyewitnesses can be helpful, but investigators need to take caution in their questioning techniques and the reliability of the information obtained.  Here is one of many publications by Dr. Brian Cutler, explaining this phenomenon, Mistaken Identification.

  • Swiss Cheese StubbornnessDon’t you dare poke holes in my theory.  I’ll just put some gouda on it and make it that much sharper.

Somebody attempts to find an issue in your plan, you find an even stronger way to defend it.  This bias is obvious if you pay attention to social media political discussions (which will drive you insane.)  If there is an alternative explanation to your theory of the crime, investigate it before you disregard it.  Often, we do the opposite and dig our feet deeper into the sand on any issue that may be challenged.

  • The Patriots PrejudiceIf I don’t like you, you must be guilty.  I don’t know what you did wrong yet, but it’ll happen – in the meantime I’ll be randomly testing the air pressure of your tires.

Yes, my bias is apparent in the labeling of the above.  I apologize to any Bostonians I’ve offended – but you have plenty of hardware to be proud of – so get over it.  More seriously, issues like racial, cultural, religious and gender biases still exist and are, unfortunately, prevalent in some investigations.  It could be a subject we had prior negative experience with or somebody we simply don’t like for whatever reason.  If you are unable to set aside your personal bias, then you need to set aside the investigation for a professional to handle.

  • Minimal Effort EffectWait a second, you want me to do what?  I’ve already got a solid theory and a completed project, now I’m expected to do more work just to find a better way – no, thank you.

This falls into the “we’ve always done it that way” mindset, or any bias that favors the easiest way to get something done versus the right way to achieve the best result.  Re-interviewing witnesses, taking time to investigate the evidence or even potentially changing the entire theory of the crime takes time and effort.  However, what takes more time and effort is doing it wrong the first time and then having to go back and do it again.  The best and most accurate results come with dedicated effort and ethical intent.

  • Friends in High PlacesHe’s the top sales performer, she’s my best friend, he would never act like that, there must be a valid explanation… most importantly, we can’t lose a person in that position.

I’ve seen this personally in multiple cases, ranging from fraud or theft to sexual harassment and discrimination.  Ignoring a complaint or excusing the evidence because the accused person is a high-valued employee or a high-ranking official is unethical and inexcusable.  For more examples, see any of the latest headlines around athletes abusing their spouses or kids.

  • “I did It” – I’m Done – I told you so.  Confession received, sale made, project completed, and the hand has been won.  I knew I played it right, because I won the pot, so I’ll play it that way every time now on.

The ends justify the means, right? No.  A confession does not end an investigation, it merely begins the next phase.  Validate the confession by conducting a thorough investigation, substantiating the details and allowing further evidence to either corroborate or disprove the accuracy of the confession.  Challenge the confession by going back through the interview to identify when the subject provided admissions that were not contaminated by the interviewer.  James Trainum explains this process in his incredible book, How Police Generate False Confessions.

Winning a poker-hand with a 7-2 off-suit may have been all luck and no skill – be careful playing it the same way next time.  For my poker friends, check out Annie Dukes’s book, Thinking in Bets.


Don’t agree with any of the above? Well, you’re probably wrong.  Joking aside, I challenge you to recognize your own biases. Slow down and look at an investigation objectively focusing on reliable information and facts.  Overcoming biases does not happen immediately or completely, but it is something we should all be aware of and be comfortable getting uncomfortable in a discussion about it.