Dr. Warner attempted to remove a Goa'uld that had infested Major Charles Kawalsky. The operation appeared to be successful but it turned out that the part that was removed was only a dead husk. (SG1: "The Enemy Within") Several months later, after a foreign body was discovered attached to the heart of Cassandra, the sole survivor of Hanka, he performed exploratory surgery on her and was able to scrape some samples of the device for biopsy. He was unable to remove the device because it was booby-trapped by Nirrti to kill the girl if there was any tampering with it. (SG1: "Singularity")