Mercer (15-9, 8-3 Atlantic Sun Conference) has won 12 straight at home in Hawkins Arena.
After Kordario Fleming's layup gave Jacksonville the lead 58-57 with 8 seconds left, Hall went one of two from the foul line to send the game into overtime.
Tied 62-62 in overtime, Hall's layup put the Bears ahead 64-62 with 1:54 left, but Javon Dawson answered with two free throws to tie it again 64-all.
After a turnover by Jacksonville's Russell Powell, Smith made a 3-pointer with 30 seconds left to put the Bears on top 67-64. Dawson missed a 3-pointer with 3 seconds.
Jarvis Haywood led Jacksonville (12-13, 7-5) with 13 points and Fleming added a double-double, 10 points and 11 boards.
Myron Medcalf and Amin Elhassan discuss the Kings' selection of Malachi Richardson with the 22nd overall pick.
Myron Medcalf and Amin Elhassan discuss the Hawks' selection of DeAndre Bembry with the 21st overall pick.
Myron Medcalf and Amin Elhassan discusses the Nets' selection of Caris LeVert with the 20th overall pick.