P.R. Laws tit. 19, § 656
(a) A person whose failure to exercise ordinary care substantially contributes to an alteration of an instrument or to the making of a forged signature on an instrument is precluded from asserting the alteration or the forgery against a person who, in good faith, pays the instrument or takes it for value or for collection.
(b) Under subsection (a) of this section, if the person asserting the preclusion substantially contributes to the loss by failing to exercise ordinary care, such person will be responsible for the loss to the extent to which the failure of each to exercise ordinary care contributed to the loss.
(c) Under subsection (a) of this section, the burden of proving failure to exercise ordinary care is on the person asserting the preclusion. Under subsection (b) of this section, the burden of proving failure to exercise ordinary care is on the person precluded.
History —Aug. 17, 1995, No. 208, § 2-406; Aug. 31, 1996, No. 176, § 2.