Face it: it was Jay

(1) Jay was in vicinity of Hae’s last-known location at the time that she went missing; and (2) Jay has no alibi for where he was during that time period.

From: http://viewfromll2.com/2014/11/23/serial-a-comparison-of-adnans-cell-phone-records-and-the-witness-statements-provided-by-adnan-jay-jenn-and-cathy/