Skip to main content

With private brokers tapping into genetic genealogical databases like and 23andme, police no longer need an exact match between crime-scene DNA and a suspect’s. A close match is enough to get them started

Open this photo in gallery:

Illustration by The Globe and Mail/SOurce: iStock

Shortly after Detective Michelle Moffatt joined the Calgary Police Department’s cold-case sexual-assault unit in 2012, she began looking into a crime that had been puzzling investigators for over 20 years.

On May 4, 1991, a terrified 28-year-old woman had called 911 at 1:30 a.m. “I just got raped,” she told a dispatcher. “A guy came and broke into my house.” Her attacker was masked, she said, and had already fled into the night.

Seven squad cars and a canine team arrived, but police found no sign of the man. Around 4 a.m. they brought the woman to a hospital, where a doctor recovered traces of the attacker from her body. But a police investigation went nowhere, and he was never caught.

More than two decades later, most of what Det. Moffatt had to work with was contained in some paper files and three evidence boxes. Among their contents were some of the woman’s clothing, a cassette tape of the 911 call, and crucially, semen swabs from the night of the rape – a treasure trove of DNA evidence, which police had lacked the technology to examine thoroughly in the 1990s.

Over the next few years, Det. Moffatt sent the old evidence out for new rounds of forensic analyses, including DNA tests. But those produced only what police know as a “Male One” DNA profile – a readout of the suspect’s genetic pattern and gender.

Because police had no idea who the suspect might be, and because the DNA wasn’t an exact match with any other genetic profiles in their records of previous offenders, Det. Moffatt had no way of connecting that information to a name. The DNA evidence was useless, in the same way a crime-scene fingerprint is useless without a criminal’s fingerprint to compare it to.

“It was at that stage where I was kind of at a dead end,” she said.

The crime would have stayed the attacker’s dark secret forever had it not been for a technique known as investigative genetic genealogy, which allows police to use private companies’ databases of genetic information to track down suspects in a new way: through their family trees.

The method has only recently begun to gain purchase in law enforcement agencies around the world. Although police and prosecutors in the United States now routinely use it to send killers and rapists to jail, it has been used much less frequently in Canada.

Several prosecutors and police officials who spoke to The Globe said they were aware of only four cases in which the technique had led to criminal convictions in this country. All of them reached their conclusions in the past year, with guilty pleas. Det. Moffatt and her partner, Detective Trish Allen, are responsible for solving two of them.

Open this photo in gallery:

Calgary police detectives Trish Allen, left, and Michelle Moffatt helped solve a 30-year-old cold case with the help of genetic information databases.Todd Korol/The Globe and Mail

The two Calgary detectives say their mission is to never let sexual violence go unpunished. “We focus on the most violent ones. Stranger attacks. Unsolved. Home invasion – basically the worst of the worst,” Det. Moffatt said.

Det. Allen began working on the 1991 case when she joined the cold-case unit in 2017, and at first there were no breakthroughs. The next year, though, a high-profile arrest in the United States revolutionized the cold-case profession.

In Sacramento, in 2018, U.S. police arrested a man in his 70s for 13 homicides and scores of rapes committed in California between 1974 and 1986. The identity of the person behind the notoriously brutal crime spree had remained unknown for so long that he had eventually earned a nickname: the Golden State Killer.

Like Det. Moffat, cold-case police in California began by examining DNA left at crime scenes. But they ran into the same problem she did: their databases of DNA drawn from convicted sex offenders didn’t contain a match, so there was no way to tie the DNA to a name. In other words, the Golden State Killer could not be caught because he had never been caught.

Open this photo in gallery:

Joseph James DeAngelo, 72, was identified by DNA evidence in 2018 as the serial predator dubbed the Golden State Killer.FRED GREAVES/Reuters

Then the American police tried a more roundabout line of inquiry. They began trying to find out how their “Male One” profile fit with information from direct-to-consumer DNA companies.

The names of these companies are well known to Canadians. Websites such as and 23andme have encouraged millions of people to send in saliva samples, which the companies use to draw up genetic family-tree profiles.

While Ancestry and other major players in the consumer DNA industry say they never hand over customer data to police, there are private data brokers who specialize in doing just that. They ask individual clients of consumer DNA companies to consider volunteering their genetic profiles to pooled databases that are open to law enforcement searches.

Police can use these databases to find people whose DNA is similar to DNA collected at crime scenes. When two people have similar genetic material, there’s a high likelihood they have family members in common.

Searching the databases creates forests of genetic family trees that police can walk through without warrants, usually with help from expert consultants.

And knowing who a criminal’s relatives are is an incredibly powerful thing: it doesn’t immediately identify a culprit, but it can narrow a field of suspects to a small number of people, allowing investigators to zero in on a target with relative ease.

With genetic genealogical databases at their disposal, police no longer need an exact match between crime-scene DNA and a suspect’s DNA, like a fingerprint to a finger. A close match is enough to get them started.

This method of turning close DNA matches into arrests is what’s known as investigative genetic genealogy. And it’s why we now know that the Golden State Killer is Joseph James DeAngelo. His unmasking was international news, but to cold-case detectives it was something else as well: an advertisement for a new technique that could crack some of the cases they had previously written off as hopeless.

Websites such as and 23andme have encouraged millions of people to send in saliva samples, which the companies use to draw up genetic family-tree profiles. George Frey/Reuters

When Canadian police want to perform DNA-based investigations, they typically have to turn to the National DNA Databank, an RCMP-controlled database. But the databank is a skewed sample: it only contains genetic profiles collected in the course of police work, including those of convicted criminals.

And the way police can use that information is limited by federal law. Detectives who query the databank are only given information on people whose genetic profiles exactly match crime-scene DNA samples. And police are forbidden from using the databank to search for suspects’ family members. These legal restrictions are intended to protect Canadians’ genetic privacy.

But Canada has no such restrictions when it comes police use of private DNA databases. And so, in 2019, Detectives Moffatt and Allen turned to Parabon Nanolabs, a DNA-analysis contractor that has sold its services to several Canadian police forces.

By applying genetic genealogy techniques, the company was able to use crime-scene DNA from the 1991 case to help identify people who appeared to be the culprit’s family members.

The detectives spent months trying to fine-tune the picture.

“I started learning genealogy myself,” Det. Allen said.

At times, she would call up people not suspected of any crimes themselves, asking them to upload their DNA files, or to allow police to view that information. Slowly, the detectives eliminated false matches and began to home in on the attacker’s family line.

In interviews, the detectives would not go into greater detail about their techniques. They would say only that their work and that of expert consultants led them to focus on specific suspects.

By October, 2020, the cold-case team believed they knew who had committed the rape. Thomas Craig Brodie was in his late 40s, meaning he was the right age to have been the attacker, and he matched the victim’s description of her assailant. Records showed he had lived near the home where the assault took place. He was a teenager at the time.

But nothing the detectives had learned through genetic genealogy could be used as proof in a criminal court. What they had was just a hypothesis.

They put in a formal request for help from their colleagues at the Calgary Police Strike Force Unit, which specializes in surveillance of suspects.

In December, 2020, plainclothes officers were on the hunt. They had the suspect’s description and were out to covertly acquire what’s known as castoff evidence.

Open this photo in gallery:

In December 2020, plainclothes Calgary Police officers were on the hunt for Mr. Brodie. They had the suspect’s description and were out to covertly acquire what’s known as castoff evidence.Jeff McIntosh/The Canadian Press

In this type of operation, a team of police officers discreetly watches a suspect until he tosses away something with spit on it – a coffee cup, say, or a Coke can. Once police have a sample of a suspect’s bodily fluid, they can use it to analyze his DNA and find out if it matches genetic material collected at a crime scene. If there is a match, that means the investigation no longer hinges on a genealogical hypothesis. At that point, police have physical evidence tying a suspect to a victim, which can be powerfully persuasive in court.

In December, the pursuit of Mr. Brodie hit a setback. His castoff sample came back from the RCMP’s central forensics lab with a note that said it didn’t contain enough genetic information to compare it to the samples from 1991.

The cold-case detectives called in the strike force on him again the following spring. This time, there was no need to dig through garbage. When Mr. Brodie spit on the ground, officers swooped in and scraped his expectoration directly off the pavement.

This time, there was a perfect DNA match.

In 2021, the detectives started drawing up arrest plans and swearing DNA warrants, necessary steps before they could ask a judge for permission to have their suspect submit to a blood DNA test when he was brought in for questioning.

“Even though that castoff has confirmed it is the offender, we still do that DNA warrant,” Det. Moffatt said.

Blood being taken during a police interview can give a suspect much to ruminate upon when a detective confronts him with news that authorities have his semen and saliva. The crushing weight of such evidence sometimes elicits on-the-spot confessions.

It was decided that Det. Allen would lead the interview, a job she relishes. She was also in the process of reaching out to the victim, to prepare her for the possibility that she would be called as a witness in any court proceedings.

This sort of outreach is a delicate task, which is why Det. Allen saves it for late in an investigation, when a suspect’s capture seems certain. For a victim, knowing their attacker is about to be reintroduced into their lives can be extremely disturbing.

Det. Allen has had the surreal experience of calling up several victims from the 1980s and 1990s who thought police had forgotten their cases. A stunned silence usually greets her when she reveals to them that a rapist has been identified, and that a decades-old case will be heading to court.

It’s news that can cause memories to resurface. A woman in her 60s might feel fresh dread at the prospect of being compelled to testify in court about something terrible that happened when she was in her 20s. “Foremost I always say to them: ‘Michelle and I will always be there every step of the way,’ ” Det. Allen said. “‘You’re never going to be left alone.’”

In July 2021, police brought Mr. Brodie in for questioning. After pricking his finger to get a sample of his blood, they cautioned him that he didn’t have to speak to them. They didn’t need a confession, but an admission of guilt can make court proceedings easier for police, and for victims.

Det. Allen confronted Mr. Brodie. She told him she knew the secret he had harboured since he was 18 years old: that he was the masked man behind the 1991 attack.

Mr. Brodie opened up. He gave a detailed accounting of the violence he had unleashed on that night, 30 years before. He told Det. Allen to tell the victim he felt sorry for what he had done.

According to the agreed statement of facts in the case, he told Det. Allen he had been drinking in a strip club. He saw the victim through a window in her house as he was walking home. “He gained access to the house through a basement window,” the statement says. “He covered his face with his T-shirt. He kicked through the door. He forced sex on her.”

He is scheduled to be sentenced on Sept. 7. During his guilty plea last year, his victim filed an anonymous impact statement.

In it, the woman said she appreciated the persistence of police, but that the resurrection of the case had caused her to reflect on how a single act of violence had rippled out over the years into financial hardship and divorce. “I rarely go anywhere alone whether it be going for a walk, to the store, or even driving to work,” she said. The attack, she added, had made her an overprotective parent.

And the fear never really went away. “On May 4th, 1991 I was sentenced to life for a crime I did not commit,” she wrote. “I still sleep with lights on all over the house.”

“Every time I walk by the basement stairs I feel compelled to glance down them to be sure no one is coming up them.”

Criminal convictions like this one appear to validate genetic genealogy as a crime-fighting technique. But, as more cases that rely on these investigative methods come to Canadian courts, not all of the accused will plead guilty. Some are sure to challenge the legality of the new way of gathering evidence.

Privacy officials are already counselling Canadians not to use direct-to-consumer DNA sites if they want to preserve their family’s genetic privacy. And it may not be long before Parliament is asked to square genetic genealogy with legislated strictures surrounding other kinds of DNA investigations. In the U.S., some state legislatures have passed laws constraining the use of the technique by police.

For Detectives Moffatt and Allen, genetic genealogy has only begun to yield results. The other of the two cases they’ve solved with the method came to a head shortly before they closed in on Mr. Brodie.

The culprit, Patrick Zamora, had on separate occasions in 1981 raped two women in bushes beside one of the parking lots at Calgary’s Foothills Medical Centre. Police had never been able to learn his identity until the detectives began to trace him through his family’s genes. When the strike team collected one of his used cigarette butts in 2020, Calgary Police confirmed that the DNA in his saliva was an exact match with that of the attacker.

After four hours of questioning, he broke down and confessed. He’s now serving a five-year prison sentence.

“He said he knew it was going to happen one day,” Det. Allen said.

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.

Your Globe

Build your personal news feed

Follow the author of this article:

Follow topics related to this article:

Check Following for new articles