  We present three methods to check CTRSs for non-confluence: (1) an ad hoc
method for 4-CTRSs, (2) a specialized method for unconditional critical pairs,
and finally, (3) a method that employs conditional narrowing to find
non-confluence witnesses. We shortly describe our implementation of these
methods in ConCon, then look into their certification with CeTA, and finally
conclude with experiments on the confluence problems database (Cops).
