This critical review examines the use of Magnetic Resonance Imaging (MRI) in detecting deception and assessing pain, two complex psychological and physiological states that have historically challenged both clinicians and researchers. Despite MRI's potential, its application in these areas invites both scientific admiration and ethical scrutiny. The review begins with a historical perspective on the evolution of MRI technology and its early adoption for studying brain patterns related to deceit and pain. It highlights the methodologies employed in key studies, summarizing their findings and pointing out the prevailing challenges and limitations. This review also covers the technical and ethical controversies surrounding the use of MRI in legal contexts, particularly in lie detection, and its clinical implications in pain management. Furthermore, it provides a comparative analysis between the uses in deception and pain, discussing overlaps in technological challenges and research findings. Finally, the review speculates on future directions for MRI technology, emphasizing the need for technological advancements and a refined ethical framework. The comprehensive analysis not only showcases MRI's capabilities but also emphasizes the complexities and responsibilities that come with its use.