In the appeal on 18 June 2004, de Berk's conviction for the seven murders and three attempted murders was upheld. The crimes were supposed to have taken place in three hospitals in The Hague: the Juliana Child Hospital (JKZ), the Red Cross Hospital (RKZ) and the Leyenburg Hospital, where de Berk had worked earlier. In two cases the court concluded that there was proof that de Berk had poisoned the patients. Concerning the other cases the judges considered that they could not be explained medically, and that they must have been caused by de Berk, who was present on all those occasions. The idea that only weaker evidence is needed for the subsequent murders after two have been proven beyond reasonable doubt has been dubbed chain-link proof by the prosecution and adopted by the court. At the 2004 trial, besides a life sentence, de Berk also received detention with coerced psychiatric treatment, though the state criminal psychological observation unit did not find any evidence of mental illness.