https://www.nbcnews.com/news/us-news...t-her-n1140696

On an October morning in 2018, Eleanor Holmes and her husband left home to run an errand and found two men inside their front gate. They introduced themselves as detectives from Orlando, Florida, and said they needed the couple?s help.

Standing in the driveway, the casually dressed detectives said they were trying to identify someone who?d been found dead many years earlier, the Holmeses recalled. They were looking for the person?s relatives, and were using DNA and genealogical records to stitch together a family tree that they hoped would lead them to a name. Friendly and businesslike, they said they?d already got DNA samples from Eleanor Holmes? sister and an aunt. And now they wanted hers.

Holmes already knew about the detectives? visit to her sister. It worried her that someone in her family had died without anyone knowing about it. She had relatives in Orlando, including a niece whom she hadn?t heard from in more than a decade. So she agreed.

?I just did it because that was the only thing on my mind, my niece. That was it, bottom line,? Holmes said in a recent interview.

The detectives, still standing in the driveway, swabbed Holmes? cheek and put the sample in a container. They thanked her, gave her a business card and drove away.

She thought nothing of it until a few days later, when she got a frantic phone call from the girlfriend of one of her sons, Benjamin Holmes Jr. Orlando police had just arrested him for allegedly fatally shooting a college student, Christine Franke, in her Florida home in 2001. They?d used DNA and genealogical records to tie him to the crime.

In that panicked moment, it dawned on Holmes that the detectives hadn?t told her the truth. They?d used her DNA to help build a case against her son.

?When they arrested him, I knew they were lying,? Holmes said. ?They lied to us.?

Police have said that the arrest of Benjamin Holmes Jr., 39, shows their commitment ?to do everything we can to solve crimes.? Franke?s family says the arrest has given them long-needed answers about her death and allowed them to stop wondering if the killer was still out there, free to prey on others.

Benjamin Holmes Jr. and his parents, though, say he is innocent. He has pleaded not guilty, and his trial, scheduled for June, may be the first to explore how police conduct investigations using genetic genealogy, a largely unregulated technology that has exploded in popularity in recent years.

Holmes and her husband, who are both in their mid-70s, aren?t the only ones in their family who feel misled by police. In the months before taking her DNA, Orlando detectives visited more than a dozen of her relatives in Florida and Georgia. Several said they were told a similar story before agreeing to provide DNA samples.

?It was just deception, not only to me but all my other family members, because they know what they were looking for when they took the DNA,? Holmes said. ?They weren't looking for someone in our family that had been killed, or that was dead. They were looking totally to find out whether or not our DNA coincided with Benjamin's. That's what they were looking for.?

For 17 years, Orlando police detectives had tried to figure out who killed Franke. Although the case had gone cold, each did what they could with the available technology and manpower. But every lead, every potential clue found at the scene, left them, and Franke?s family, without answers.

?I thought they?d never catch him,? Franke?s mother, Tina, 70, said.

Franke, 25, was one of four siblings raised in Vero Beach, outside Orlando. An aspiring elementary school teacher, she was studying at the University of Central Florida while working as a server at a restaurant near the Universal Orlando theme parks. She lived with her girlfriend about a half hour away, on the north side of town.

Early in the morning of Oct. 21, 2001, after working a double shift, Franke returned home to an empty apartment; her girlfriend was out of town. Later that day, after the girlfriend was unable to reach her, she called a neighbor, who found Franke dead just inside the apartment door.

She?d been shot once in the head, and her wallet, containing no cash, had been discarded on the floor, according to court documents. Her clothing had been partially removed, and investigators found semen on her body. Police surmised that she had resisted the killer?s attempts to rob and rape her.

Police took a sample of the semen and submitted it to the state crime lab, which developed a profile and entered it into a national criminal database. There was no match. They took DNA from dozens of people ─ potential suspects, as well as friends, relatives, co-workers, neighbors, acquaintances and witnesses ─ and compared their profiles to the DNA found at the scene. Again, no hits.

They tried other forensic methods ─ lifting fingerprints from the apartment, entering a shell casing into a national firearms database ─ and found nothing. Years passed with no progress.

That changed in April 2018, when California authorities announced that they?d used a groundbreaking technique to identify a man they said was the Golden State Killer, a serial rapist and murderer who?d terrorized the state in the 1970s and the 1980s. Law enforcement officials said they?d solved the case by entering crime-scene DNA into an online database called GEDmatch, where people shared profiles purchased from direct-to-consumer genetic testing companies such as Ancestry.com and 23andMe.

Orlando Detective Michael Fields, who inherited the Franke case from a retired colleague in 2012, decided to try the same tactic. He reached out to a Virginia company, Parabon NanoLabs, which had just started helping law enforcement identify unknown suspects by using genealogy websites to find their relatives and build family trees. The researchers, led by Parabon?s top genealogist, CeCe Moore, found two cousins of the suspected killer in GEDmatch and traced their common ancestors to a husband and wife who lived in Valdosta in the first half of the 1900s.

The Valdosta couple had an extremely large family, producing a sprawling family tree. Navigating that thicket left Fields and the researchers at dead ends, unable to go further without getting DNA from more people in the family.

Asking innocent people to voluntarily provide their DNA ? known as ?target testing? ? is an unseen but essential, and thorny, component of investigative genetic genealogy. While police are seeking straightforward information about family ties, the process can also reveal secrets, including out-of-wedlock births and adoptions, ethics and privacy experts say. Subjects may not fully understand how their DNA profiles will be used.

While American courts have ruled that police are allowed to mislead people to obtain evidence, there?s a debate within law enforcement over how honest police should be in seeking DNA from people who aren?t suspected of a crime.

Investigator Matt Denlinger works cold cases for the Cedar Rapids Police Department in Iowa. He used target testing to help solve the 1979 murder of a teenage girl. He says the truth, without including many details, usually works.

?You just go up and tell them what you?re doing. No sleight of hand,? he said. ?Most people are happy to help. They know they?re not involved. People get excited to help solve a mystery, if you phrase it that way.?