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Minnesota Criminal Defense & Forensic Law Firm
Injustice Anywhere is a Threat to Justice Everywhere
Serving Southwest Minnesota
We Accept the Following Forms of Payment:
Injustice Anywhere is a Threat to Justice Everywhere
Serving Southwest Minnesota
We Accept the Following Forms of Payment:
Injustice Anywhere is a Threat to Justice Everywhere
When most people hear the term forensic science, they think of hard, objective facts—DNA matches, fingerprints, ballistics, and digital evidence that seem indisputable. On television, forensic experts are portrayed as neutral scientists who simply “follow the evidence.”
In reality, forensic science is performed by human beings—and humans are subject to cognitive bias. This hidden influence can shape how forensic evidence is interpreted, presented, and ultimately used against a defendant in court.
If you’re facing criminal charges, understanding how bias affects forensic science—and hiring a defense attorney who knows how to challenge it—could make all the difference in your case.
Cognitive bias doesn’t mean a scientist is corrupt or dishonest. It refers to the unconscious mental shortcuts and assumptions that influence how people perceive and interpret information. Even well-trained forensic experts are vulnerable to these psychological effects.
In a forensic investigation, bias can affect:
What an examiner notices when reviewing evidence
How they interpret ambiguous results
How confidently they testify about their findings
When an analyst is told that a suspect confessed or that witnesses identified the defendant, they may—without realizing it—interpret scientific data in a way that supports that narrative. This is known as confirmation bias, and it’s one of the most common forms of cognitive bias in forensics.
Several types of bias can influence forensic conclusions. Here are the most common forms that defense attorneys encounter:
The tendency to interpret evidence in a way that confirms existing beliefs or theories. For instance, if an examiner knows police believe a suspect is guilty, they may (unconsciously) see a partial fingerprint or partial DNA profile as a “match.” This is why it is so important for your defense attorney to reviewing the underlying information the lab received in your case to know if they were exposed to information that could impact confirmation bias.
When analysts are exposed to background case information—such as “the suspect already confessed”—their interpretation of the evidence may become skewed in favor of that narrative. This may mean that an analyst is more willing to consider things like drop out even if a suspects genetic marker or markers may not be present at all locations.
If investigators only submit evidence they believe is incriminating, the forensic analysis starts on uneven ground. Missing or ignored samples could have supported the defense. It is not uncommon for a lab to only take certain samples that were sent up by law enforcement and test them, leaving others uninterpreted. It becomes important for your defense attorney to know this, especially if the analyst is making decisions about what items of evidence to test and what items of evidence not to test.
Once an examiner forms an initial opinion, they may “anchor” to it and resist revising their conclusion, even as new information emerges. This is not an uncommon phenomenon to see in labs that are owned and run by law enforcement agencies where analysts commonly see themselves as being part of the prosecution team, not a true neutral scientist.
Experts may overstate the certainty of their conclusions in testimony, giving jurors the impression that ambiguous or partial evidence is definitive. This can be especially problematic when dealing with difficult or degraded samples, especially complex mixtures, where the potential for bias increases as analysts are more likely to be swayed by other information.
Forensic evidence carries enormous weight in courtrooms. Jurors tend to view it as infallible “hard science.” But when cognitive bias shapes forensic conclusions, the consequences can be catastrophic.
1. Wrongful Convictions
Many wrongful convictions have been overturned because forensic experts overstated their findings or allowed bias to guide their interpretation. Once a lab report says “the DNA matches the defendant,” it becomes extremely difficult to undo—even if the conclusion was flawed.
2. Misleading Testimony
Jurors rarely understand the limitations of forensic testing. When an expert affected by bias testifies with unwarranted certainty, it can unfairly sway the verdict.
3. Skewed Investigations
Bias at the forensic level can narrow investigations. Once analysts focus on a single theory, other suspects or explanations may be ignored.
4. Cumulative Bias
Bias can stack across the system—investigators, prosecutors, and forensic scientists may all share the same assumptions about guilt, leaving defendants at a significant disadvantage. This gets compounded when labs are run by state law enforcement agencies, such as in Minnesota.
Cognitive bias is not hypothetical—it has influenced real cases across the U.S. and the world.
Brandon Mayfield Case (2004): After the Madrid train bombings, the FBI incorrectly linked attorney Brandon Mayfield to a partial fingerprint. Once the identification was made, examiners became anchored to it, even ignoring evidence that contradicted the match.
Innocence Project Cases: Many wrongful convictions later overturned by DNA testing involved forensic experts who misinterpreted or overstated evidence—claiming, for instance, that a hair “Matched” a suspect when the science only showed it was “consistent with.”
Amanda Knox: in Italy, police and prosecutors developed a theory early on of what occurred and then looked for evidence that supported their theory while ignoring exculpatory evidence. Cognitive bias played a huge role in the prosecution of Amanda Knox (who after years in prison was finally vindicated).
Adam Scott: In the UK, Adam Scott was falsely accused and prosecuted for a sexual assault he did not commit. His DNA showed up in a sample because the lab analyst reused a plastic tray that had his DNA in it for an entirely different reason. That same tray was then used to test a swab taken from the rape victim. The fact that the trays had been reused had been identified almost two weeks before the prosecutor charged him, but bias resulted in the charging of Mr. Scott even with the knowledge of plates being reused.
These cases demonstrate how even skilled professionals can make serious errors when bias enters the forensic process.
If you’re facing criminal charges involving forensic evidence, your defense attorney must know how to expose bias and human error in the scientific process. Here’s why that matters:
A strategic defense can uncover and counter forensic bias in several ways:
1. Hire Independent Experts
Defense teams can bring in unbiased forensic specialists to review the evidence independently and identify errors or overstatements.
2. Limit Contextual Influence
Attorneys can challenge whether the prosecution’s experts were exposed to unnecessary case details that may have shaped their interpretations.
3. Emphasize Ambiguity
Highlight that many forensic tests—such as DNA mixtures, toolmarks, or fingerprint comparisons—involve subjective interpretation, not absolute certainty.
4. Challenge Overstated Testimony
Through careful questioning, defense counsel can show that an expert’s confidence exceeded what the data actually supported.
5. Educate the Jury
By explaining cognitive bias in plain language, the defense can help jurors evaluate forensic evidence more critically and fairly.
Forensic science should protect the innocent, not contribute to injustice. But when cognitive bias enters the process, even well-intentioned scientists can help convict the wrong person.
A strong criminal defense lawyer will:
Demand transparency in forensic testing
Retain independent experts to verify results
Cross-examine prosecution experts effectively
Educate the jury about the limits of forensic evidence
Without these safeguards, a defendant’s fate may rest on biased science rather than objective truth.
Cognitive bias in forensic science is one of the most overlooked threats in the criminal justice system. It doesn’t imply dishonesty—just humanity. Every expert brings subconscious assumptions into their work, and those assumptions can mean the difference between conviction and acquittal.
If you or someone you love is facing charges based on forensic evidence, don’t assume the science is beyond challenge. Work with a criminal defense attorney experienced in forensic bias cases—someone who understands both the science and the psychology behind it.
When you have been charged with a crime, you do not have to face the charges on your own, nor do you have to pay the maximum consequences.
If you are facing a criminal matter or a family law matter, we can help you find a satisfactory resolution to your case. From divorce and child custody issues to theft and DWI, you will have a powerful and knowledgeable advocate in your corner. To learn what we can do for you, call 507-822-5735to schedule a free consultation.
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