Vann was charged with the murders of Anith Jones, 35, and Afrikka Hardy, 19, in October, 2014.
Vann was arrested in his Gary, Ind., home after Hardy's body was discovered in a Hammond motel room. Police connected him to Hardy quickly, as he had arranged a meeting with her through Backpage.com, a website popular with prostitutes and their clients.
Vann allegedly told police he was surprised and impressed he had been caught so quickly.
In the initial days after his arrest Vann was highly cooperative and talkative with police, leading them to six more bodies before he abruptly stopped cooperating.
Three of those bodies were identified as Jones, 28-year-old Teaira Batey and 36-year-old Kristine Williams. With Martin's identification, five of Vann's alleged seven victims have been identified.
The Lake County coroner's office is working on identifying the remaining two victims.