Patch 3.2.0 (04-Aug-2009): Now properly triggered by periodic critical strikes. In addition, the tooltip incorrectly stated that 20% damage is reflected, when it is actually 10%. Tooltip fixed.
Patch 3.1.3 (2009-06-02): This talent now deals 5/10% of the critical strike damage taken by the paladin back at the attacker.
Patch 1.10.2 (02-May-2006): Will now properly produce its damage effect on the attacking caster.