Forensic analysis is often viewed as highly accurate, a belief reinforced by numerous crime television shows where ballistic and blood-spatter experts reveal crucial evidence to apprehend suspects.
However, this belief has permeated into legal settings, where the precision of forensic analysis is seldom scrutinized, as highlighted by recent research.
Both ballistic and blood spatter analyses, which assess evidence from crime scenes, are based on scientific principles. Yet, practitioners frequently draw conclusions in court that exceed the support of their empirical findings, according to researcher Sara Gordon—who notes that these assertions are not adequately challenged by lawyers and judges.
“These analyses are accepted primarily because they have always been approved, and there’s an assumption regarding their reliability,” states Gordon, an associate professor at the Peter A. Allard School of Law at the University of British Columbia.
Expert testimony regarding forensic evidence can offer “substantial assistance” in clarifying specific case details, according to a fact sheet from the Department of Justice. For decades, Canadian courts have permitted its inclusion in legal proceedings.
Gordon analyzed Canadian cases to investigate the forensic and investigative methods that frequently influence evidence accepted in courts.
Her study on firearms evidence reveals “considerable methodological flaws” in the research supporting ballistics as a field, potentially “underestimating error rates.” She concludes that experts often fail to provide courts with the complete context and present a “misleading impression” of their accuracy.
Evidence markers are placed beside shell casings on the street outside a cafe that was shot at in Surrey, B.C., in August 2025. (Darryl Dyck/The Canadian Press)
Bullet proof?
To associate a bullet or casing found at a crime scene with a specific gun caliber, ballistic experts will compare bullets or casings fired from test weapons and scrutinize them under a microscope for common features.
Eventually, a forensic scientist may be called to testify in court that the evidence from a crime scene either matches or does not match, referencing research from their field to support their claims.
Gordon notes that examiners often assert that the error rate in ballistics is between one and two percent. However, the studies she reviewed for her research indicated error rates as high as 50 percent.
She also points out that there are no established standards for the minimum number of similarities necessary to confirm a bullet match.
“It’s primarily a subjective analysis,” she explained.
Researcher Sara Gordon asserts that legal professionals have grown ‘accustomed’ to viewing ballistics and blood spatter analysis as dependable evidence, while experts fail to fully disclose the accuracy of their field when testifying.
Her research, which follows similar assessments of forensic evidence in the United States, references a 2021 case in Ontario where a firearms examiner admitted under cross-examination that her conclusion—that shell casings from a crime scene matched a gun found in the accused’s residence—was subjective.
The examiner further stated that there was “no specific number of agreements required between two items for her to determine that there was a match,” and she based her opinion on her belief that a match was “within the limits of practical certainty.”
The matter was highlighted in a Chicago courtroom in 2023, where a judge, citing a lack of “objective forensic based reasons,” prohibited the use of ballistic matching in a criminal trial.
The judge subsequently reviewed a dozen other cases that resulted in wrongful convictions due to flawed ballistic matching, calling it a “wake-up call to courts operating as rubber stamps in simply accepting this type of evidence.”
Bullet fragments are displayed on a screen in a Utah courtroom on July 9, during a preliminary hearing for Tyler Robinson, who is accused in the fatal shooting of Charlie Kirk. (Spenser Heaps/Pool/The Associated Press)
Building on such rulings, Gordon contends that some ballistic experts should refrain from testifying in cases where the science does not allow them to draw definitive conclusions.
A senior forensic scientist who frequently provides testimony in court believes that being open about the limitations of a discipline is crucial.
Darryl Barr, who analyzes firearms and tools associated with crimes for Bulletproof Forensic Consulting, asserts that there is “a scientific basis for firearms examinations” and substantial empirical evidence backing experts’ conclusions—though he acknowledges that they could improve in clarifying this in court.
Barr expresses confidence in the widespread use of forensic analysis in judicial processes globally and states that any examination of his field is appreciated.
“Science advances through scrutiny, and forensic science is no different,” he remarked.
Investigators gather ballistic evidence at two separate crime scenes. Left, New York police photograph bullets on the sidewalk where Brian Thompson, CEO of UnitedHealthcare, was fatally shot on Dec. 4, 2024. Right, the copper jacket of a bullet found near the scene of a shooting close to the White House on May 24 this year. (AP Photo/Stefan Jeremiah / AP Photo/Alex Brandon)
The CSI effect
One of the responsibilities of both prosecution and defense attorneys is to critically evaluate each other’s evidence. However, the accuracy of forensic science is seldom examined, according to Gordon.
She believes part of the issue stems from society’s perception that ballistics and blood spatter are as conclusive as DNA evidence and can uncover vital information in investigations—partly due to crime dramas like Law and Order and numerous CSI spin-offs.
For instance—despite what a suave, fictional detective might claim—the science of blood spatter cannot determine whether or not an individual acted intentionally.
A physical comparison supervisor at the Vermont Forensic Laboratory examines a shell casing in March 2015. (Wilson Ring/The Associated Press)
Gordon’s independent research on blood spatter analysis discovered that some experts provide very detailed testimonies, such as speculating about an accused’s mental state.
She cites a case from British Columbia in 2009, where the prosecution used blood pattern analysis from a crime scene to reconstruct the defendant’s actions, claiming he had guilty intent based on how blood was “projected” during the incident.
“There are no studies validating or establishing an error rate for conclusions regarding a person’s mental state based on bloodstain patterns,” she writes in her research.
“The science does not support making those kinds of conclusions,” she informed CBC News.
‘Frailties of the evidence’
The risk of legal professionals not challenging expert witness testimonies is acknowledged in case law, according to Rebecca McConchie, president of the Trial Lawyers Association of British Columbia.
Additionally, the danger of judges and juries failing to recognize the “frailties of the evidence when evaluating it,” she remarked in a statement to CBC News.
“It is essential for individuals to maintain an open mind regarding criminal justice matters or evidence presented as definitive proof of a person’s guilt,” McConchie emphasized.
A statue of Themis, goddess of justice, at the B.C. Supreme Court in Vancouver, pictured on Oct. 6. (Nav Rahi/CBC)
In conclusion, Gordon asserts that Canada has received less attention in legal literature, and she hopes her studies will enhance the courts’ ability to determine guilt or innocence.
She aims to provide insights into the evidence supporting forensic claims, enabling lawyers and judges to ask more critical questions—to “present it in a manner that encourages a more skeptical view of the evidence.”
A representative for the RCMP, which offers forensic services throughout Canada, indicated awareness of the research and reiterated its commitment to employing established scientific methodologies, quality assurance protocols, and professional standards in its operations.