Obvious parallels to the BTK murders. Taunting letters to police demanding credit, sometimes including driver's licenses. 911 call giving the address of a victim. A long break in the killings. Self gratification during a slow strangulation. (Josephine Otero) A poem to an intended victim who didn't arrive when he expected. (Anna Williams, "Oh Anna Why Didn't You Appear") In this episode the poem was entitled "Oh Cassandra why are you so late".
The episode title refers to an actual incident in the biblical Book of Judges (Judges 12:5-6), in which the correct pronunciation of a particular word ("Shibboleth") became a life-or-death test.
When Goren and Eames visit Keith Durbin's parole officer, she says of him, "He reminds me of that guy from the space movie...y'know, where the thing comes out of his chest?" This is a reference to the classic horror film Alien