See: https://issues.jboss.org/browse/SOA-3409 The same code is in BRMS 5.2 - we will want the fix for SOA-3409in BRMS 5.2 too.
This issue should be the same as Bug 724443 - (BRMS-388) Decision Table: String Index Out Of Range
*** This bug has been marked as a duplicate of bug 724443 ***