Keister had 14 points and 10 rebounds as the Crusaders (6-17, 3-5 Patriot League) ended a three-game winning streak by knocking Lafayette (14-9, 5-3) out of a tie for first in the conference.
The Leopards fell one game behind Lehigh (15-8, 6-2), which defeated American U. 77-65 on Saturday.
Holy Cross took a 44-31 lead before Lafayette closed the gap to 44-37 with 15:52 left. The Crusaders then went on a 13-0 run in the next 6 minutes to put the game away, capping the spurt on Evans' layup with 9:59 remaining.
Lafayette would get no closer than 17 points the rest of the way.
Ryan Willen led Lafayette with 14 points.