Cognitive errors are common thought processes or mental biases that lead us astray and cause us to make bad decisions if left unchecked.
One cognitive error that has significant negative ramifications for many professions, including law, is confirmation bias.
Confirmation bias refers to our natural inclination to seek out information that supports our beliefs and to ignore and sometimes suppress any information that does not.
Simply put, once we form a belief we have a tendency to close our minds to new evidence that suggests an alternative conclusion, no matter how compelling that new evidence may be.
Consider the danger of this cognitive error in the context of a police investigation when an officer develops a premature belief that a particular individual (your client) has committed a crime. There is a concern that the officer may overlook or ignore other potential sources of evidence that may alter the course of the investigation. The investigation may subsequently become a search for evidence that confirms the officer’s pre-existing belief in your client's guilt, rather than a search for evidence to discover what really happened.
Confirmation bias is also a concern for the prosecution. A prosecutor’s independent assessment of an investigation and the evidence may be compromised if he or she is too closely aligned or influenced by the beliefs or views of the police and/or the complainant.
Defence counsel plays an important role in the criminal justice system in Canada by looking at the case from another perspective to ensure that other avenues of investigation are not overlooked.