Who is Sergeant Barbara Havers from A Great Deliverance and what is their importance?

Sergeant Havers is thirty years old, and "a decidedly unattractive woman." Havers has "fine, shiny hair," which she wears in an unflattering "bowl" cut. Her mouth is thin, her eyebrows are "[heavy and] unplucked" and her eyes are especially small. Barbara Havers wears no makeup and her mouth seems to be "pressed permanently into a disapproving frown." She is described in the narrative as a woman who is "stubby, sturdy, and entirely unapproachable" (pg. 20.) Havers' brother Tony died of leukemia at a young age. Havers' mother and father never visited their son in the hospital, claiming it was too wrenching to see their son in that condition.