A cognitive bias is something that keeps you from seeing reality as it is. Instead, the bias, which may be perfectly natural, causes you to see the world as you expect it to be.
For example, most people suffer from confirmation bias. When we see new information that confirms what we already believe, we tend to trust that information. When new information is provided that contradicts what we already believe, we tend to discount it. In that way, many of us fail to take in true information that tends to contradict what we already believe.
Confirmation bias is simply a normal way we process information, although a somewhat problematic one. There are over 180 known types of cognitive bias where one's existing beliefs, motives and the situation affect the person's judgment and conclusions.
There is a specific type of cognitive bias among forensic analysts called "forensic confirmation bias." It occurs when certain information that is unnecessary to their analysis is introduced. Examples include the defendant's race and previous criminal record. Exposure to that information has been shown to bias forensic analysts one way or the other.
Yet many forensic analysts have a blind spot about their potential biases. A 2017 survey found that, while many analysts did know that outside information might bias their analyses, they denied that their own conclusions could be affected.
At the same time, the survey found that many other analysts had not been trained in how cognitive biases operate. Therefore, they did not know how to reduce the effect in their work. So, some analysts had been trained on cognitive bias but discounted its effect, while others had not been trained at all.
Exposure control can reduce forensic confirmation bias
The primary method for reducing cognitive bias among forensic analysts is simply to avoid exposing them to extraneous information that could bias them. The 2016 President's Council of Advisors on Science and Technology report urged "blinding" forensic analysts to potentially biasing information throughout the course of criminal cases.
This is typically done by having case managers who are responsible for excluding extraneous information from the forensics team. Unfortunately, although exposure control is a standard approach in most scientific areas, forensic analysts have not uniformly used it.
Forensic analysts are supposed to be neutral. They are not an arm of the police or prosecutor's office. However, some forensic analysts show a marked bias towards the prosecution.
If criminal trials are to be fair, the forensic evidence must be examined by people who understand that they are acting in the interest of science, not working to convict someone. That includes doing what is necessary to eliminate cognitive biases that could affect their conclusions.