This section is from the book "A Commentary On The Law Of Contracts", by Francis Wharton. Also available from Amazon: A Commentary On The Law Of Contracts.
It is not necessary, however, that complicity should be shown by proof of an express combination between the parties.2 "When two persons, in correspondence with each other, are apparently pursuing the same object, in part by the same means, one performing part of an act, the other completing it, for the attainment of the object, the inference of complicity may be drawn.3 But the use of unlawful means to carry out an agreement does not necessarily stamp the agreeraent with illegality.1 - It is admissible to prove by extrinsic facts that a contract, however innocent in terms, is illegal either by statute or by common law.2 It may be also shown that the consideration was immoral or illegal by statute.3 - It is sufficient if illegality is established by a preponderance of proof. It is not necessary to establish it beyond reasonable doubt.4 But the burden of proof is on a party seeking to set up the illegality of a transaction.5
Complicity and illegality to be in-ferentially shown and by preponderance of proof.
1 See McGavock v. Puryear, 6 Cold. 34. In Gaylord v. Soragen, 32 Vt. 110, an action for selling liquor in bulk in New York, where the sale was legal, to be retailed in Vermont, where the sale would be illegal, Aldis, J., said: "Although mere knowledge of the unlawful intent of the vendee by the vendor will not bar him from enforcing his contract to recover for the goods in our courts, yet it is well settled that if he in any way aid the vendee in his unlawful design to violate our laws, such participation in the illegal enterprise will disqualify him from maintaining an action on his contract in this state. The participation by the vendor must be active, to some extent; he must do something, though indirectly, in furtherance of the vendee's design to violate our laws. Mere omission to act is not enough; but positive acts in aid of the unlawful purpose, however slight, are sufficient." See to same effect Green v. Collins, 3 Cliff. 494; Aiken v. Blaisdell, 41 Vt. 656; Tuttle v. Holland, 43 Vt. 542; Hill v. Spear, 50 N. H. 253. - In Adams v. Couillard, 102 Miss. 167, Colt, J., said: "Clearly it is not enough if he has only reasonable cause to believe that a violation of law is intended." In Webster v. Munger, 8 Gray, 587, Thomas, J., said: "The distinction is sound between a case where a seller simply has knowledge of the illegal design - no more - and where he makes a sale with a view to such design, for the purpose of enabling the purchaser to effect it." In Green v. Collins, 3 Cliff. 494, Judge Clifford argues with great force that mere knowledge of future illegal use does not vitiate, unless it is an ingredient of the contract that the law should be violated, or the seller combines with the purchaser to violate the law; citing to this effect Sortwell v. Hughes, 1 Curt. 245. To the same point the learned American editor of Benjamin on Sales, sec 511, note u, cites Harris v. Runnels, 12 How. U. S. 79; Smith v. Godfrey, 28 N. H. 379; White v. Buss, 3 Cush. 443; Peck v. Briggs, 3 Denio, 107; Tracy v. Talmage, 14 N. Y. 173; Curtis v. Leavitt, 15 N. Y. 15; Cheney v. Duke, 10 Gill & J. 11; Rindskopf v. De Ruyter, 39 Mich. 1; Bishop v. Honey, 34 Tex. 245.
2 R. v. Parsons, 1 W. Bl. 392; R. v. Whitehouse, 6 Cox C. C. 38; Aiken v. Blaisdell, 41 Vt. 658; Foster v. Thurston, 11 Cush. 322; Kelley v. People, 55 N. Y. 566; Bloomer v. State, 48 Md. 521; and see s. on Ev. sec 7.
3 See Wh. Cr. L. 8th ed. sec 1398 et seq.
 
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