Porque após o teste positivo inicial de Boomer (que Baltar esconde para salvar seu pescoço), e Baltar depois descobrindo que cada amostra levará ~ 11 horas para testar, ele fixa o detector de cylon para dar a todos um passe.
The functioning Cylon detector created by Baltar confirms that Sharon Valerii is indeed a Cylon, a fact that Baltar hides from Valerii, fearing what her Cylon persona would do were he to tell her (TRS: "Flesh and Bone"). After discovering that it would be easier for him to make all the results "green," Baltar alters the device to mimic this method of thinking (TRS: "Tigh Me Up, Tigh Me Down"). However, after Sharon Valerii shoots Commander Adama, everyone believes the Cylon detector to be a failure, thinking that it did not pick up her Cylon nature (TRS: "Resistance", "He That Believeth In Me").