Reasonable Doubt: Credibility in court and your behaviour

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      In the last installment, Kevin Yee wrote about the history of oaths to tell the truth and why we still swear oaths before giving evidence in court. 

      In a trial, besides arguing points of law and how they should be interpreted, the entire purpose is to get to the truth. In the courtroom, there can be nothing more important than getting to the truth, the whole truth, and nothing but the truth.

      When we are evaluating whether or not someone is telling the whole truth, we are assessing their credibility. In giving evidence, there is nothing more critical than your credibility, and your entire case could turn on your credibility versus the credibility of the opposing side.

      Credibility means more than finding out who is the liar and who is the saint. Yes, there are liars out there who will consciously lie under oath, but often two opposing litigants will both subjectively believe that their memory of events is correct, although one (or both!) will simply have a flawed memory. A judge is doing more than trying to suss out whether or not a witness is lying; he or she is also assessing if an honest witness’s memory can be trusted.

      So what do judges look at when they are assessing credibility? How can you increase your credibility? How do people decrease their credibility?

      Every judge is going to be a bit different, but there are some guidelines every litigant can try to follow to increase their credibility.


      This, by far, is the most important thing, because we cannot read minds. On cross-examination, the opposing lawyer is going to try to find as many inconsistencies in your evidence as possible, as well as see how you react and deal with information and evidence that contradicts your testimony. The purpose of cross-examination is to test your evidence and see how your consistency stands up.

      Also important to note: the consistency of your story will be considered from the very beginning of your case to the moment you are in court. Any savvy opposing party will bring to the attention of the court any changes in your story that occurred prior to court. Then, in court, your testimony will be examined in and of itself to see if you say two or three things that cannot be true at the same time.


      Remember the “whole truth” part of the oath? Well, courts operate on the presumption that you are going to be transparent. This starts from the part of the process in all noncriminal cases when litigants must disclose anything relevant to their cases. If you fail to disclose relevant and important information, this will be a serious mark against your credibility.

      If it looks at all like you’re hiding something or refusing to answer or dodging questions when you’re on the stand, this will seriously detract from the credibility of anything else you do or say. The opposing lawyer cross-examining you will be rubbing her hands with glee when you start refusing to answer questions. Of course, there are limits to having to answer questions: the questions must be on a topic that is relevant to the case. But keep in mind, the bar for relevance is very low.

      Keeping evidence logical

      Your testimony must make sense. Now this is where things can get difficult: what may make sense to you for a person from your background and culture may not make sense to a judge of a different background and/or culture. This aside, before you start your case, think about your story critically from the point of view of someone who has never heard it before. Do your story and/or actions make sense? If not, why is that? Can you address a weakness in your case by conceding a point?

      History in the case of abiding by court orders/following rules of court

      The minute you start doing silly things like evading service of court documents, not following court rules, not disclosing evidence, and breaching court orders, your credibility is diminished forevermore. These actions show the court that you do not have much respect for its process and a judge is less likely to believe that you are going to take your oath to tell the truth seriously.

      Avoiding erratic or inappropriate behaviour/facial expressions in court

      When you’re in a trial, you’re going to be sitting through the opposing party’s case. This means you will be listening to evidence that you believe is not true or is offensive to you. Often the other party’s evidence will cut you to your core and it will be very hard to hear.

      The minute you start making facial expressions, sighing, standing up and shouting at the judge or witness, or storming out of the courtroom, you are giving a negative context to the judge in which to assess your evidence. Nobody likes this behaviour during a trial and it will be used against you. 

      A good rule of thumb is to keep in mind that anytime you enter a courtroom, you are being watched and assessed. Behave in a way that is consistent with the evidence you want to give the court.

      With respect to the litigant that is blatantly lying and does not just have a flawed memory, you may want to consider a study pulished in 1991 in American Psychologist by Paul Ekman and Maureen O’Sullivan. The article was called “Who can catch a liar?” The study evaluated 509 people to see who could tell if someone was lying. They included law-enforcement personnel (from the US Secret Service, the CIA, the FBI, the DEA, police, and judges, as well as college students, working adults, and psychiatrists. The participants were shown a series of 10 videos of people describing their feelings while watching a scene on TV, and they were told that half the subjects were lying. At the end of each video, the participants were asked to determine whether or not the person in the video was telling a lie or the truth.

      The only group of people that were able to determine who was lying better than 50 percent of the time (chance) were the Secret Service agents.

      Judges will have more than a short clip to be able to assess your credibility while in court, and so it may be that their rates of accuracy in determining who is blatantly lying will be higher in these settings.

      Regardless, if your case relies solely on your credibility and you know the other side to be a liar, you may want to consider whether or not it’s worth it to roll the dice in court.

      A word of caution: you should not act or rely on the information provided in this column. It is not legal advice. To ensure your interests are protected, retain or formally seek advice from a lawyer.

      Laurel Dietz practises family law and criminal defence with Dogwood Law Corporation in Victoria, B.C. Reasonable Doubt appears on on Fridays. She can be followed on Twitter at You can send your questions for the column to its writers at