Operational definitions and evidentiary readiness for XR, digital twins, virtual worlds and metaverse-like systems in...

Extended reality (XR), three-dimensional reconstructions, digital twins, virtual worlds and metaverse-like environments are increasingly proposed for forensic and legal medicine, yet the field - including our own earlier contributions - is fragmented by heterogeneous terminology and aspirational claims that are rarely specified in a verifiable manner. This ambiguity undermines reproducibility, impedes comparison across studies, and risks premature courtroom use of visually persuasive but insufficiently validated reconstructions. Here we propose an operational, anti-hype taxonomy that distinguishes extended reality (XR: virtual, augmented and mixed reality), digital twins, virtual worlds, and metaverse-like environments in ways that are actionable for forensic workflows. We define what is and what is not 'metaverse' in a forensic context by specifying minimum evidentiary criteria: persistence, synchronous multi-user interaction, identity/role management, interaction traceability (audit trail), and interoperability or at least portable state capture, all under explicit data governance. We then map functional categories (training and competency maintenance; scene investigation; autopsy and post-mortem imaging augmentation; injury documentation and reconstruction; courtroom visualisation; remote collaboration and teleforensics) to typical medico-legal workflows, identifying where spatial technologies can add measurable value and where they introduce non-trivial risks, including perceptual and cognitive biases, error propagation from acquisition and registration, and threats to provenance and chain of custody. Finally, we articulate minimum 'evidentiary readiness' requirements and a research agenda to move the field from demonstrations to evidence-grade systems: benchmark datasets, uncertainty quantification, black-box/ground-truth validation studies, human-factors evaluations, and standardised reporting and governance. This vocabulary and taxonomy are intended as a shared baseline for authors, reviewers, laboratories and courts considering XR and metaverse-like tools in forensic settings.