Forensic analysis has a reputation for being reliably accurate, an assumption that’s been polished by many crime TV dramas where ballistics and blood-spatter teams uncover essential evidence to catch the perpetrator.
But that assumption has found its way into courtrooms, where the accuracy of forensic analysis is rarely questioned, according to new research.
Both ballistic and blood spatter analysis, which examine evidence from a crime scene, are grounded in science. But its practitioners regularly make conclusions in court that are far beyond what their own empirical evidence supports, says researcher Sara Gordon — while lawyers and judges don’t challenge those conclusions enough.
“They’re admitted largely because they’ve always been admitted and people just sort of assume that they’re reliable,” says Gordon, an associate professor at Peter A. Allard School of Law at the University of British Columbia.
Qualified and admissible expert testimony on forensic evidence can provide “significant assistance” in understanding specific information in a case, a fact sheet from the Department of Justice says. Canada’s courts have allowed it to be included in cases for decades.
Using Canadian cases, Gordon examined these forensic and investigative techniques that informed evidence regularly admitted in court.
Her analysis of firearms evidence points to “significant methodological flaws” in the research that backs up ballistics as a discipline that may “underestimate error rates.” She concludes that experts often don’t give courts the full story and give “a false impression” of the accuracy of their speciality.
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 connect a bullet or casing found at a crime scene to a caliber of gun, ballistics examiners will compare other bullets or casings shot from test guns and examine them under a microscope to look for similarities.
Eventually a forensic scientist may end up in a courtroom testifying that the evidence found at a crime scene is or isn’t a match, citing research from their field to back up their conclusions.
Gordon says examiners will often testify that the error rate of the ballistics field is somewhere between one and two per cent. But the studies she examined for her research reported an error rate as high as 50 per cent.
She also says there are no set standards for the minimum number of similarities needed to match bullets.
“It’s largely a subjective analysis,” she said.
Researcher Sara Gordon says lawyers have become ‘accustomed’ to treating ballistics and blood spatter analysis as reliable evidence, and that experts don’t give a full account of how accurate the science is when testifying in court.
Her research, which follows similar audits of forensic evidence in the United States, cites a case in Ontario in 2021, where a firearms examiner conceded under cross-examination that her conclusion — that shell casings from a crime scene matched a handgun found in the accused’s apartment — was subjective.
The examiner later added there was “no specific number of agreements required between two items for her to conclude that there was a match” and she formed her opinion because she believed a match was “within the limits of practical certainty.”
The issue came to a head in a Chicago courtroom in 2023, where a judge, moved by a lack of “objective forensic based reasons,” banned the use of ballistics matching in a criminal case.
The judge then reviewed a dozen other cases that resulted in a wrongful conviction from flawed ballistics matching, labelling it a “wake-up call to courts operating as rubber stamps in blindly finding general acceptance” of 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)
Drawing from such decisions, Gordon argues that some ballistic experts shouldn’t be testifying in cases where the science doesn’t give them the ability to draw conclusions.
One senior forensic scientist who regularly testifies in court says being transparent about a discipline’s limitations is key.
Darryl Barr, who examines weapons and tools linked to crimes for Bulletproof Forensic Consulting, maintains there is “a scientific basis for firearms examinations” and plenty of empirical evidence that supports experts’ determinations — but he concedes they could do better at making that clearer in court.
Barr says he’s reassured by the fact that virtually every country in the world uses forensic analysis as part of its judicial process, and adds that any scrutiny of his discipline is welcomed.
“Science improves through scrutiny and forensic science is not any different, obviously,” he said.
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
Part of a prosecution or defence counsel’s role is to scrutinize each other’s evidence. But digging into the accuracy of the science of forensic evidence doesn’t happen often, says Gordon.
She thinks part of the reason is that society at large has come to think ballistics and blood spatter are as definitive as DNA evidence and can reveal crucial details in an investigation — in part due to crime shows like Law and Order and the many spin-offs of CSI.
For example — despite what a slick, sunglasses-wearing fictional detective might say — the science of blood spatter cannot indicate if a person was acting deliberately or not.
A physical comparison supervisor at the Vermont Forensic Laboratory examines a shell casing in March 2015. (Wilson Ring/The Associated Press)
Gordon’s separate research on blood spatter analysis found the detail to which some experts testify is sometimes very specific, such as inferring what an accused’s mental state might have been.
She points to a B.C. case from 2009 where the Crown used analysis of blood patterns in a crime scene to reconstruct the actions of the accused, arguing he had guilty intent because of the way blood was “projected” during the attack.
“There are no studies testing or establishing an error rate for conclusions about an individual’s mental state based on bloodstain patterns,” she writes in her research.
“There’s just no indication, in the science, that we can make those sorts of conclusions,” she told CBC News.
‘Frailties of the evidence’
The danger of lawyers not challenging expert witness testimony in court is recognized in case law, says Rebecca McConchie, president of the Trial Lawyers Association of British Columbia.
So, too, is the risk of judges and juries not appreciating the “frailties of the evidence when assessing it,” she said in a statement to CBC News.
“It is so important for people to keep an open mind when they hear about criminal justice issues or evidence held out as obvious proof of a person’s guilt,” McConchie said.
A statue of Themis, goddess of justice, at the B.C. Supreme Court in Vancouver, pictured on Oct. 6. (Nav Rahi/CBC)
Ultimately, Gordon says, Canada has received far less attention in legal literature and she wants her studies to make the country’s courts better at doing their job of determining guilt or innocence.
She says her work is about providing information about the evidence behind the evidence for lawyers and judges to be able to ask more questions — to “lay that out for them in a way that just makes them view the evidence a little bit more skeptically.”
A spokesperson for the RCMP, which provides forensic services across Canada, said it was aware of the research and that it’s still committed to using established scientific methodologies, quality assurance processes and professional standards in its work.
Source: www.cbc.ca
