Dr. Keffler was a rogue NID Bio-geneticist who created Anna, a Goa'uld/Human hybrid who he created out of the DNA from the Goa'uld Sekhmet as a science experiment to unlock Goa'uld secrets. He was the son of a Nazi war criminal who had stolen the artifacts of Sekhmet from France during the war .
He defended his actions by pointing out that Stargate Command never expressed significant concern over the hosts of the Goa'uld they fought (Unconcerned about the obvious distinction between killing the host to prevent the symbiote committing further atrocities and actually giving a symbiote a host).
He was eventually killed by Anna in revenge for his actions as she sensed an 'evil' within him greater than even the evil that dwelt within her in the form of Sekhmet, Anna subsequently killing herself to stop Sekhmet from taking control again. (SG1: "Resurrection")