Despite the P300‐Concealed Information Test's validity in detecting concealed memory when it is conducted immediately after the mock crime, whether the P300‐CIT's detection efficiency is moderated by time delay remains unknown. Here, we conducted a mock crime study in which guilty participants were tested immediately after the mock crime or 1 month later. An innocent group was also tested. Assuming that the autobiographical Implicit Association Test (aIAT) and the P300‐CIT rely on nonoverlapping mechanisms for memory detection, participants were tested using both the P300‐CIT and the reaction time (RT)–based aIAT. Results suggested that the sensitivity of both tests remains even after the 1‐month delay. The indicators from the RT‐aIAT and P300‐CIT were uncorrelated, thus combining P300‐CIT and aIAT data further increased the efficiency of memory detection.