Research with P300 is proceeding at an exciting rate. P300 ERP lie detection that has been proven effective might bring important, even revolutionary benefits to society, at least if used in proper situations. Ineffective testing can only be harmful. It is important that this technology be used if and only if its effectiveness has been rigorously established. If it is proven effective, our society will then face difficult questions on how to use the technology in ways that maximize its benefits and minimize its costs, while respecting individual rights.