fair opportunity to litigate their claims.” Pa at P.R. Laws Ann. tit. 31, § 3343, provides in pertinent part: “[i]n order that the presumption of the res judicata may be valid in another suit, it is necessary that, between the case decided by the sentence and that in which the same is invoked, there be the most perfect identity between the things, causes, and persons of the litigants, and their capacity as such.” Although this provision refers to res judicata, it has also been applied for purposes of collateral estoppel. See Baez-Cruz v. Municipality of Comerio, 140 F.3d 24, 29 (1998). Similarly, the requirement of mutuality — that there be the “most perfect identity” between the parties — has also been relaxed. Id.; Schneider v. Colegio de Abogados, 670 F.Supp. 1098, 1103 (D.P.R.1987) (<HOLDING>). Accordingly, when an issue “essential to the
holding that even without satisfying the perfect identity of persons things and issue a party may still invoke collateral estoppel holding that collateral estoppel applies to  1983 claims recognizing the doctrine of collateral estoppel in agency proceedings holding collateral estoppel elements met considering changed circumstances in the context of an exception to the general rule of collateral estoppel holding that the party against whom collateral estoppel is asserted must have been a party to the prior action