Longtime newscaster Paula Zahn will focus her next Discovery network true-crime episode on the local mystery of Tammy Jo Alexander, the teenager found fatally shot in a Livingston County cornfield in 1979 whose identity remained unknown for 35 years. Zahn has hosted the true-crime series "On the Case with Paula Zahn" since 2009, focusing each hour-long episode on a single case or mystery. Whoever killed Tammy Jo Alexander, shooting her twice then leaving her body in the cornfield, is still unknown. The Livingston County Sheriff's Office is still investigating the case. Tammy Jo's sister, Pamela Dyson, said by telephone that she hopes the show could prompt someone with information to come forward.