If this device could be used to extract intelligence from belligerent detainees without the use of torture, what then? Used on an accused serial killer, and the suspect shown sites where bodies had been found to see if he recognized them? If they knew the victim? You wouldn't be able to lie anymore. Use of such a device would be covered under unreasonable search and seizure. There are abuses of that now, I don't see how this device would magically make such abuses more prevalent.
And don't worry, Aunt Spiker, if the technology proves itself it will get out and be used for therapeutic purposes at the very least.