The word "estoppel" has meanings which vary by application. Ordinary "equitable estoppel" entails detrimental reliance by one party, but "judicial estoppel" does not. (See Edwards v. Aetna Life Ins. Co. (6th Cir. 1982) 690 F.2d 595, 598 distinguishing the two, "Unlike equitable estoppel, judicial estoppel may be applied even if detrimental reliance or privity does not exist"; Jackson, supra, 60 Cal. App. 4th at pp. 182-183.)
In California, judicial estoppel has been justified because it prevents fraud on the courts and will "prevent injury to an innocent litigant." ( In re Marriage of Dekker (1993) 17 Cal. App. 4th 842, 850 21 Cal. Rptr. 2d 642.)
In some jurisdictions, judicial estoppel requires a prior success on the fact asserted. In this respect, it works as a corollary to issue preclusion.
This assumes the estoppel works, if at all, only in subsequent litigation or proceedings, but this is not always so. (See Schulze v. Schulze (1953) 121 Cal. App. 2d 75, 83 262 P.2d 646 "The defendant may not play fast and loose with the court in this fashion.
He cannot in one breath say the judgment is valid,--obtain relief thereby; and in the next, say it is invalid. Having relied on the validity of the judgment of divorce on the first motion, he is estopped from thereafter claiming it is void.".)
The doctrine " ' "is invoked to prevent a party from changing its position over the course of judicial proceedings when such positional changes have an adverse impact on the judicial process. . . ." ' " (Jackson, supra, 60 Cal. App. 4th at p. 181.)
" 'It seems patently wrong to allow a person to abuse the judicial process by first advocating one position, and later, if it becomes beneficial, to assert the opposite.' " (Ibid.; see id. at pp. 183-184, fn. 8 "circumstances may warrant application of the doctrine even if the earlier position was not adopted by the tribunal".)
The principle is not limited to successive actions. (See Pegram v. Herdrich (2000) 530 U.S. 211, 227, fn. 8 120 S. Ct. 2143, 2153, 147 L. Ed. 2d 164, 180 "Judicial estoppel generally prevents a party from prevailing in one phase of a case on an argument and then relying on a contradictory argument to prevail in another phase"; Allen v. Neal (1965) 217 Tenn. 181, 186-187 396 S.W.2d 344, 346-347; Ray v. Midfield Park, Inc. (1972) 289 Ala. 137, 142 266 So.2d 291, 295-296.)