The Reaction Time-Based Concealed Information Test (RT-CIT) was designed to detect familiarity with crime-related information. However, RT-CIT results can be manipulated by preparing innocent-looking responses for these probes. We developed a new paradigm allowing us to assess such response preparation processes. In each trial of the task, a crime-related prime question was presented, followed by a test item which was either a publicly known item, an irrelevant item, or a probe. The test item could either match the question in terms of content or not, and a key had to be pressed if the answer was not publicly known (Go-Nogo task). In two experiments (total N = 138), we found evidence for both familiarity (slower reactions toward crime-related than unrelated information) and response preparation effects (less errors for probes matching the prime question) in guilty participants, indicating that the new paradigm can help to overcome problems of strategic response preparation.