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Ground-penetrating radar (GPR) produces non-distinct regions of increased signal scatter when scanning perched water in a shallow sandy loam soil. This scatter phenomenon occurs due to the soils increased electrical conductivity, which exponentially increases with its water content, thereby increasing signal degradation. Radar signal scatter is presently being targeted as a perched water indicator for site-specific agricultural applications. This article reports on a critical verification method developed to examine the effectiveness of using the traditional procedure in manually interpreting GPR images for the detection of perched water. A blind test procedure found human perception classification errors in the preliminary studies. Critical evaluation testing revealed that the image interpreters prior knowledge had unknowingly influenced image classifications. Rigorous blind testing of subjective manual interpretation of complex GPR images was determined essential prior to reporting successful GPR investigations. Project results illustrate that blind tests help insure against possible false interpretations and reporting when using this technology. This critical evaluation procedure also demonstrated a need to develop automated classification procedures when analyzing complex GPR images, rather than relying solely on manual interpretations.