<p>A simple diagnostic testing procedure is described to help non-expert practitioners search for unmarked graves at historic burial sites using ground-penetrating radar. The methodology, which includes real-time video-assisted documentation of GPR apparatus trajectories, is illustrated with data from a historic cemetery in Texas, USA. The acquired radargrams are classified, from which unmarked-grave decisions are made under strict, moderate, and lax thresholds. Since there is no gold standard, an alternative strategy for decision-making is adopted assuming the distribution of radar signatures generated by the marked graves is the same as the distribution generated by the unmarked graves. About half of the marked graves generated no discernible radar signature, so this proportion of the unmarked graves is likely to be missed. About one-third of the marked graves generated the tell-tale signature of a deep-seated hyperbola so this proportion of the unmarked graves is likely to be found. The remaining signals are complex and ambiguous. The uncertainty is due to the wide variety of radar signatures that are expressed by burials. The diagnostic testing procedure allows a non-expert practitioner to develop acuity in recognizing unmarked-grave signatures and hone a decision-making capability that leads to improved stakeholder trust.</p>