Zatarc programming is very difficult to detect, the only known means being recent Tok'ra technology which uses a modified memory recall device and is similar to a lie detector. It reads the subconscious mind and compares it to the conscious memory. Originally created to verify information retrieved from the torture of captured Goa'uld prisoners, the prototype zatarc detector was unproven technology. It could misread omissions as false memories, and it falsely identified programming in O'Neill and Carter.
An experimental procedure using the same device can counteract the programming by damaging the portion of the brain affected by the zatarc technology. The counter-programming technique was used on Lieutenant Astor, but was unsuccessful, and she took her own life. The zatarc detector will reveal any lie or deception whether someone is a zatarc or not, however hostility and strong emotions can throw off the readings. It was used at the Alpha Site in an effort to identify a murderer, but the results showed false positives and were unreliable.
As the technology has been gradually modified, it has been used more reliably in special situations as a lie detector. The zatarc detector was used on Shifu and was able to determine that he is indeed the Harsesis. A modified version of the zatarc detector was used to interrogate a captured Kull Warrior. The device revealed the images in the warrior's mind in a holographic display that allowed SG-1 to determine the warrior's home planet of Tartarus. Technology similar to the zatarc detector was used by Athena to probe Vala's subconscious mind as she searched for the buried memories of Qetesh. The procedure was extremely painful, perhaps made worse by Vala's resistance, and glimpses of memories were displayed on a monitor as they were accessed.
Cross Reference: Anise, Artok, Lieutenant Astor, Major Graham, Holographic Projection, Kull Warrior, Memory Recall Device, Tok'ra, Trust, Zatarc
Episode Reference: Divide and Conquer, Absolute Power, Allegiance, Evolution, Memento Mori