Response to Letter to the Editor Regarding “A bibliometric analysis of investigative genetic genealogy in academic literature: Trends, networks, and emerging themes”

Dear Editor,

Thank you for the opportunity to respond to the letter concerning our article. We welcome this exchange and appreciate the chance to clarify the rationale underlying our search strategy, terminological choices, and the scope of interpretation of our bibliometric findings.

• 1.The nomenclature of this area remains unsettled

The correspondents are correct that terminology matters. However, the recent literature shows precisely why no single term can yet serve as an uncontested gold standard for delimiting the field. Different peer-reviewed sources use, overlap, or refine several labels, including investigative genetic genealogy (IGG), forensic genetic genealogy (FGG), forensic investigative genetic genealogy (FIGG), and even investigative forensic genetic genealogy (iFGG). Glynn [1] describes FGG as a new subdiscipline emerging at the intersection of forensic genetics, genetic genealogy, and genealogical research. Kling et al. [2] discuss IGG explicitly as a rapidly growing field of forensic science. Dowdeswell [3], by contrast, uses FGG while addressing essentially the same investigative practice. Tuazon et al. [4] make the point most directly: the law-enforcement use of genetic genealogy databases does not yet have standard nomenclature or settled scope, and the authors propose a unifying nomenclature precisely because multiple competing labels remain in use.

The volatility of the lexicon is also visible in institutional and policy documents. The U.S. Department of Justice adopted the phrase “forensic genetic genealogical DNA analysis and searching” (FGGS) in its interim policy, while NTVIC later formalized “forensic investigative genetic genealogy” (FIGG) in programmatic guidance [5,6]. More recent review literature continues to reflect this movement, with Wang et al. [7] using the terminology of “forensic investigative genetic genealogy” to describe the field's maturation. In other words, the domain is not suffering from a minor stylistic variation around a single settled term; it is undergoing active terminological consolidation. Under those conditions, it is methodologically unrealistic to assume that one phrase, however important, can function as a final and universally accepted boundary marker of the literature.

• 2.Our search strategy was reported transparently and paired with relevance screening

Because the terminology is still in motion, search design in this area necessarily involves a balance between sensitivity and specificity. Review-methods scholarship has long recognized that literature searching requires trade-offs between recall and precision, and that complex or emergent domains often call for broader retrieval followed by careful screening rather than reliance on a single supposedly definitive descriptor [8,9]. The key methodological requirement is therefore not perfection in the abstract, but transparency, reproducibility, and evaluability.

This is precisely why our article reported the database, the search fields, the Boolean string, the search date, and the screening workflow in full. That reporting choice was not incidental. It is consistent with established guidance emphasizing that search methods should be documented with enough clarity to permit appraisal, replication, and critical scrutiny [[10], [11], [12]]. Indeed, recent methodological discussions note that bibliometric and evidence-synthesis studies should be judged not only by the sophistication of their mapping software or network visualizations, but also by the transparency of their data-source selection, corpus construction, and acknowledged limitations [13].

For the same reason, the inclusion of a broader retrieval expression should not be conflated with a claim of automatic conceptual equivalence at the inclusion stage. In a transparent review workflow, a term may be used because it increases recall, while final eligibility is determined by relevance screening. In our study, records were not retained merely because they matched a search expression; they were screened for substantive relevance to investigative or forensic genetic genealogy, long-range familial searching, or law-enforcement use of genealogical DNA databases. Accordingly, the inclusion of a broader retrieval term was a recall-oriented design choice within a two-step identification-and-screening process, not a categorical assertion that every use of that phrase in every context is synonymous with the focal domain.

We fully acknowledge that the phrase “forensic genetic genealogy” is important and, in retrospect, could profitably be included explicitly in future updates or sensitivity analyses. We do not resist that suggestion. But it does not follow that the absence of one additional descriptor renders the published corpus methodologically void. In an unstable terminological environment, no search string is metaphysically perfect. The proper standard is whether the retrieval logic was declared, reproducible, and reasonably suited to the stated purpose. On that standard, we submit that our approach was methodologically defensible.

• 3.Bibliometric studies map defined corpora rather than absolute fields

A second point of clarification concerns the interpretive status of bibliometric results. The criticism in the letter appears to assume that a bibliometric analysis must function as a comprehensive and final census of an entire field. That is not how bibliometric methods are usually understood. As Donthu et al. [14] explain, bibliometric analysis is a rigorous approach for exploring large bodies of scientific literature and uncovering trends, structures, and relationships in the accumulated record. The object of study, however, is always a defined dataset. Recent guidance on evaluating bibliometric reviews similarly emphasizes that findings should be read in light of the database chosen, the query designed, the cleaning procedures applied, and the limitations openly acknowledged [13].

For that reason, our article should be read as a map of the Scopus corpus retrieved through a transparently disclosed strategy, not as a claim to have established the final ontology of the domain. This is especially true in a fast-moving interdisciplinary area such as IGG/FGG/FIGG, where the terminology, governance frameworks, and technical protocols are still evolving. To insist that a bibliometric map in such an environment must already coincide with the field in its totality would set a standard that is neither realistic nor consistent with the bibliometric methods literature.

This corpus-dependent understanding is also consistent with practice in neighboring areas of forensic science. Published bibliometric or scientometric studies have mapped forensic genetics, forensic anthropology, and forensic fibre evidence by using bounded corpora drawn from identifiable databases and explicit search designs [[15], [16], [17]]. Their scholarly value lies in the structure they reveal within the dataset they actually analyze, not in any implied claim that their corpus exhausts every possibly relevant document in existence. We submit that the same interpretive principle applies here.

• 4.The use of Scopus was conventional rather than anomalous

The correspondents also suggest that reliance on a single database may limit the corpus. At the level of general principle, that observation is fair: no bibliographic database is exhaustive, and every source has known coverage biases. The relevant methodological question, however, is not whether a database has limits - all do - but whether the selected source is widely accepted for the kind of analysis being performed and whether its use has been disclosed clearly enough for readers to assess the consequences.

On that point, Scopus is a conventional and defensible choice. Scopus and Web of Science are widely recognized as the two dominant databases in bibliometric research, with different but overlapping strengths in coverage, indexing, and citation analysis [18,19]. Comparative work frequently notes the broad coverage of Scopus, while also recognizing that database choice should be matched to the purpose of the review and that all such choices involve trade-offs. In forensic science specifically, Scopus-based bibliometric designs are not unusual; they have been used in mapping forensic anthropology and forensic genetics, among other subfields [16,17].

We therefore agree with the limited point that future work could expand the exercise by triangulating Scopus with other sources such as Web of Science, PubMed, Dimensions, or carefully structured supplementary searches. That would be a constructive extension and might illuminate database-specific variation. But it is important not to confuse a desirable extension with a prerequisite of methodological legitimacy. If one were to argue that a single-database bibliometric study is inherently invalid, a substantial proportion of the published bibliometric literature - including work in forensic science itself - would have to be dismissed on grounds not supported by prevailing practice or methodological guidance.

• 5.Use of the term IGG does not place the practice outside forensic science or outside accountability

The letter also raises a broader conceptual concern: namely, that use of the label “investigative genetic genealogy” may imply an attempt to distance the practice from forensic science and, by implication, from standards, validation, accreditation, and accountability. We respectfully do not share that inference. The current literature repeatedly describes the practice as both lead-generating and located within the broader domain of forensic science. Kling et al. [2] explicitly characterize IGG as a forensic-science field. Glynn [1] situates FGG within the forensic sciences as a new hybrid subdiscipline. Gurney et al. [20] argue for standards and certification precisely because the method has high stakes for public trust, proficiency, and accountability. These positions do not contradict one another. A method may generate investigative leads rather than direct courtroom identifications and still require rigorous scientific governance.

Indeed, recent definitional work makes this dual character even clearer. Tuazon et al. [4] describe law-enforcement genetic genealogy as a technique that produces investigational leads but still forms part of a broader forensic genetic genealogy framework. Their article also emphasizes that leads generated through such searches must ultimately be confirmed through direct forensic comparison. This is entirely compatible with the position that the practice requires strong scientific and procedural safeguards. Accordingly, we do not accept the premise that use of “IGG” in our article can be read as an effort to evade the forensic-science status of the practice or to soften the need for oversight.

Quite the contrary: one of the central themes identified in our article was governance - including validation, transparency, ethics, and legal accountability [21]. Our study did not use terminology to minimize those issues; it highlighted them as structurally important within the academic literature. The correspondents’ preference for a particular label is a legitimate intervention in an ongoing debate. But a normative preference for one term over another should not be transformed into a retrospective claim that scholarship using an alternative, but widely circulating, label is methodologically unsound.

• 6.What we accept as constructive and how the map can be strengthened

Although we defend the methodological legitimacy of our published study, we also think the letter usefully points toward future refinements. First, future iterations of the review could explicitly add terms such as “forensic genetic genealogy” and “forensic investigative genetic genealogy,” and then report the marginal yield of those additions through a sensitivity analysis. Such an exercise would be particularly valuable in a field whose terminology is still being consolidated. Second, a multi-database design could be used to compare overlap and divergence across Scopus, Web of Science, and other platforms. Third, because the field is changing quickly, periodic updates of the bibliometric map would likely be informative in their own right.

These are, however, proposals for extension rather than evidence of fatal defect. Emerging interdisciplinary areas are often mapped iteratively: one study establishes a transparent baseline corpus; subsequent work broadens the search, compares data sources, or refines terminology in light of new conventions. That process of cumulative refinement is not a sign that the first map “did not know what it was doing”; it is how responsible scholarship develops in a field whose nomenclature and professional norms are still taking shape [4,7,9,13].

For these reasons, we respectfully maintain that our article remains a valid and informative contribution. It did not claim to pronounce the final boundaries of the field. It offered a transparent map of a reproducibly retrieved Scopus corpus and interpreted the resulting structures within the limits of that design. Readers are therefore entitled to debate terminology, propose alternative search expansions, or call for cross-database triangulation - all of which we welcome. But those debates are best understood as refinements of the map, not as demonstrations that the original exercise lacked methodological competence.

1. Conclusion

We appreciate the correspondents' emphasis on terminology and agree that corpus construction deserves close scrutiny in any bibliometric study. We also agree that future work can usefully broaden and stress-test the retrieval strategy. Where we respectfully differ is on the implication drawn from those observations. In our view, the present case illustrates a familiar methodological condition of evidence synthesis in an emergent interdisciplinary area: the need to construct a transparent, reproducible, and reasonably inclusive corpus while the field's own nomenclature is still evolving.

Our study addressed that problem openly by disclosing the database, query logic, and screening procedure and by presenting the results as a bibliometric map of the resulting corpus. For those reasons, we believe the article should be read as a transparent contribution to a developing literature, not as a purportedly absolute atlas of the field. We therefore welcome further dialogue, future sensitivity analyses, and additional mapping exercises, while respectfully maintaining that our published approach was methodologically sound for the purpose it set out to achieve.