Petitioners contend that this presumption of guilt under the Fisheries Decree violates the presumption of innocence guaranteeed by the Constitution. As early as 1916, this Court has rejected this argument by holding that: "In some States, as well as in England, there exist what are known as common law offenses. In the Philippine Islands no act is a crime unless it is made so by statute. The state having the right to declare what acts are criminal, within certain well-defined limitations, has the right to specify what act or acts shall constitute a crime, as well as what proof shall constitute prima facie evidence of guilt, and then to put upon the defendant the burden of showing that such act or acts are innocent and are not committed with any criminal intent or intention." The validity of laws establishing presumptions in criminal cases is a settled matter. It is generally conceded that the legislature has the power to provide that proof of certain facts can constitute prima facie evidence of the guilt of the accused and then shift the burden of proof to the accused provided there is a rational connection between the facts proved and the ultimate fact presumed. To avoid any constitutional infirmity, the inference of one from proof of the other must not be arbitrary and unreasonable. In fine, the presumption must be based on facts and these facts must be part of the crime when committed. The third paragraph of Section 33 of P.D. 704 creates a presumption of guilt based on facts proved and hence is not constitutionally impermissible. It makes the discovery of obnoxious or poisonous substances, explosives or electricity in any fishing boat or in the possession of a fisherman evidence that the owner and operator of the fishing boat or the fisherman had used such substances in catching fish. The ultimate fact presumed is that the owner and operator of the boat or the fisherman were engaged in illegal fishing and this presumption was made to arise from the discovery of the substances and the contaminated fish in the possession of the fisherman in the fishing boat. The fact presumed is a natural inference from the fact proved. We stress, however, that the statutory presumption is merely prima facie. It can not, under the guise of regulating the presentation of evidence, operate to preclude the accused from presenting his defense to rebut the main fact presumed. [G.R. No. 119619. December 13, 1996]