23andMe

23andMe is a consumer genetic-testing company whose growing database of autosomal DNA becomes, in the book, a possible route from an unknown offender’s genetic profile to a family connection and ultimately an identity. Its significance lies in that promise and its limits: the service can connect people through relatives, but its privacy policies and terms of service barred law-enforcement cooperation, leaving Michelle McNamara to contemplate a route she could not simply use through ordinary investigative channels.

Consumer Testing and Family Connections

By 2016, commercial companies including 23andMe offered DNA testing for about one hundred dollars and a saliva sample. The tests produced autosomal DNA profiles, which could be used not only to learn about traits or possible health risks but also to identify genetic relatives. Unlike a search limited to a male lineage, autosomal testing could connect people across family lines.

The book describes how this capacity could matter to adoptees and people raised by single mothers who were trying to learn more about their origins. A database match might reveal a previously unknown cousin; that connection could provide a path toward locating a birth father or discovering other information about a person’s identity. A first search did not have to be final: as additional people uploaded their DNA, a service could notify an existing customer of newly available relatives. One example cited is an email reporting that 51 people who shared DNA with a customer had joined within the previous 90 days.

The scale of the databases made the possibility more consequential. The book gives 23andMe a total of 1.5 million profiles and Ancestry.com a total of 2.5 million. These figures are presented as a snapshot of a rapidly expanding consumer-testing landscape, not as a guarantee that any particular search would produce a useful relative. The value for an investigation would depend on whether a relevant family connection had submitted a profile and could be recognized among the results.

A Potential Investigative Route

The book distinguishes the commercial genealogy databases from official law-enforcement DNA systems. It describes CODIS as a national system built from local and state forensic databases, where crime-scene samples and certain suspect samples move through verification and comparison. Commercial services, by contrast, held large collections of consumer autosomal profiles that could potentially expose a family connection not apparent from a comparison limited to the offender’s own forensic markers.

The proposed investigative logic was indirect. Rather than expecting the unknown offender to have submitted his own profile, investigators might find a second- or third-degree cousin in a commercial database and use that relative as a lead toward identifying the offender. The book argues that submitting the killer’s actual genetic material, rather than only selected markers, could make this kind of search especially useful. It presents that prospect as a possibility, not as a completed search or a result obtained through 23andMe.

For Michelle McNamara, the idea had become a persistent research question. Her planned bucket-list tasks included figuring out a way to submit DNA to 23andMe or Ancestry.com. The databases represented a new kind of investigative resource: not another old case file, but a large and continually growing network of family relationships that might make an otherwise invisible connection visible.

Privacy, Terms, and Legal Limits

The book states that neither 23andMe nor Ancestry.com would work with law enforcement, citing privacy concerns and their terms of service. That refusal placed an institutional boundary between a potentially useful database and investigators seeking to use it. The constraint was not simply that the databases lacked scale; their size was precisely what made them attractive. The obstacle was whether law enforcement could lawfully and legitimately bring crime-scene DNA into a system built for consumer use.

The practical barrier was also technical. A customer ordinarily received a tube, provided saliva, and returned it for testing. Michelle did not have the killer’s saliva or a swab; she had a genetic profile on paper. A scientist friend of Billy Jensen’s reportedly believed there was a way around that obstacle, but the account does not describe the method or establish that it was attempted. The distinction matters: the book records an avenue under consideration, not a successful submission or a match made by 23andMe.

The ethical and legal questions remain part of the proposal itself. The discussion invokes privacy, the companies’ terms of use, and the Fourth Amendment to the United States Constitution, framing access to commercial genetic data as more than a technical problem. Michelle, according to the account, would have disregarded the services’ terms to enter the killer’s DNA. The possibility of finding a relative therefore carried a conflict between investigative promise and the rules governing how customer data could be used.

Place in the Investigation

23andMe’s role in the narrative is prospective rather than operational: it is a possible source of family leads, not an agency that investigated the case or a database shown to have identified the offender. The distinction keeps the company’s importance in proportion. Its profiles could offer a new way to move from genetic similarity to a family network, but the book supplies no evidence that the killer’s profile was ever entered or that a 23andMe customer led investigators to him.

That unrealized route nevertheless illuminates a shift in the investigation’s imagined tools. Michelle’s work also involved collecting official case materials, indexing people and places, and scanning files so that information could be searched and shared. Commercial genetic databases offered a different kind of scale: not a searchable archive of reports, but an expanding set of biological relationships. 23andMe thus stands at the intersection of consumer identity research and criminal investigation, where a tool designed to connect customers with relatives might also point toward an unknown suspect, while the company’s privacy boundaries determined whether that possibility could be pursued directly.