Anyone with solid decision will not back out except if it failed like rope cut or someone found them, i literally seen many videos of ctb and sometimes people ctb by self-immolation or slit their throats, its cruel but it depends on how really one is sure about his decision and the will to do, mostly someone will not fear or feel anything if they been on their peak of pain and hopelessness, anyone who think "i might ctb later" will no do it really and will back out on first fear thought, ctb need someone who doesn't think but act immediately