When taking a characteristic test a natural roll of 6 is always a failure, and a natural 1 is always a success, regardless of any other modifiers. However, if the model has a characteristic of 0 it automatically fails the test.
Source: Warhammer Armies Project
When taking a characteristic test a natural roll of 6 is always a failure, and a natural 1 is always a success, regardless of any other modifiers. However, if the model has a characteristic of 0 it automatically fails the test.