As it is the duty of a citizen, when required to do so, to testify in court concerning facts within his knowledge for the compensation allowed him by law, a contract to pay one who is amenable to process a further sum for his attendance as a witness is invalid, both on grounds of public policy and for lack of consideration.25 Expert witnesses, however, are held not to be subject to this rule, and a contract to pay for a statement by them of their opinions on the witness stand is upheld.28 It seems more obviously objectionable to bargain to pay a witness compensation contingent upon the success of the party to the litigation for whom the witness is expected to testify, than to contract to give additional compensation in any event, and the authorities clearly hold invalid such contingent contracts to compensate witnesses.27 Even an expert may not bargain for such contingent compensation.28 So contracts to pay for evidence of a certain nature desired for purposes of litigation have been similarly denounced.29 But contracts of employment by which the employee undertakes to render services in ascertaining facts to be used in litigation are valid.30 There is a class of cases not often referred to in this connection, where contracts somewhat analogous to contracts of contingent compensation for evidence have been upheld, generally without discussion of their legality. Offers of reward for evidence leading to the arrest and conviction of criminals are common and when complied with are enforceable.81 It is quite as objection-

Patents Co., 243 Fed. 277, aff'd 255 Fed. 242, 168 C. C. A. 202 (see also General Film Co. v. Sampliner, 252 Fed. 443, 164 C. C. A. 367), the court held that while a claim for treble damages by a person injured by a violation of the Sherman Anti-Trust Law (Act July 2, 1890, c. 647, 26 Stat. 209) is assignable, yet where a lawyer, for services that he was willing to settle for $5,000 cash, took an assignment of a claim which he thought was worth at least $75,000, the transaction was champertous, and he could maintain no action on the assigned claim, as it was taken for purposes of speculation. Cf. Rogers v. Hendrick, 85 Conn. 260, 271, 82 Atl. 586, 590.

24 See note to Huston v. Scott, 35 L. R. A. (N. S.) 729; Second American Dec. Digest, Vol. 4, p. 856. So in Alabama an attempted transfer of chattel property adversely held is invalid. Pope v. Union Warehouse Co., 195 Ala. 309, 70 So. 159.

25 Willis v. Peckham, 1 Brod. & B. 515; Dawkins v. Gill, 10 Ala. 206;

Dodge v. Stiles, 26 Conn. 463; Wright v. Somen, 125 El. App. 256; Haines v. Lewis, 54 Iowa, 301, 6 N. W. 495, 37 Am. Rep. 202; Hagan v. Wellington, 7 Eans. App. 74,52 Pac. 909; Clifford v. Hughes, 139 N. Y. App. Div. 730,124 N. Y. S. 478; Smith v. Hartsell, 150 N. C. 71,63 S. E. 172,22 L. R. A. (N. S.) 203; RamschaseTs Est, 24 Pa. Super. 262. 26 Severn v. Olive, 3 Br. & Bing. 72; Yeatman v. Dempsey, 7 C. B. (N. S.) 628; Lincoln Mountain Gold Min. Co. v. Williams, 37 Colo. 193, 85 Pac. 844; Lewis v. Blye, 79 111. App. 256; Johnson v. Pietsch, 94 111. App. 459; Barms v. Phaneuf, 166 Mass. 123, 44 N. E. 141, 32 L. R. A. 619; People v. Jefferson County, 35 N. Y. App. Div. 239, 54 N. Y. S. 782; Hough v. State. 68 N. Y. Misc. 26, 124 N. H. S. 878, In many of these cases the expert was to render services in examining the facts, or otherwise informing himself prior to the trial. Cf. Burnett v. Freeman, 125 Mo. App. 683,103 S. W. 121, 134 Mo. App. 709, 115 S. W. 488; Walker v. Cook, 33 11I. App. 561.

27 Dawkins v. Gill, 10 Ala. 206; Henderson v. Hall, 87 Ark. 1, 112 S. W. 171, 26 L. R. A. (N. S.) 70; Bowling v. Blum (Tex. Civ. App.), 52 S. W. 07. Cf. Wedgerfield v. De Bernardy, 24 T. L. R. 497.

28 Sherman v. Burton, 166 Mich. 203, 130 N. W. 667, 33 L. R. A. (N. S.) 87; Laffin v. Billington, 86 N. Y. S. 267; In re Certain Lands, 144 N. Y. App. Div. 107, 128 N. Y. S. 999, affd. without opinion, 204 N. Y. 626, 97 N. E. 1103; In re Schapiro, 144 N. Y. App.

D. 1, 128 N. Y. S. 852; Hough v. State, 145 N. Y. App. D. 718, 130 N. Y. S. 407; Davis v. Smoot (N. C), 97 S. E. 488.

29 Rees v. De Bernardy, [1896] 2 Ch. 437; Wallis v. Portland, 3 Ves. 494; Neece v. Joseph, 95 Ark. 562, 129 S. W. 797, 30 L. R. A. (N. S.) 278, Ann. Cas. 1912 A. 665; Josephs v. Briant, 108 Ark. 171, 157 S. W. 136, 115 Ark. 538, 172 S. W. 1002, Ann. Cas. 1916

E. 741; Patterson v. Donner, 48 Cal. 369; Hare v. McGue (Cal.), 174 Pac. 663, L. R. A. 1918 F. 1099; Gillett v. Logan County, 67 11I. 256; Goodrich v. Tenney, 144 111. 422, 33 N. E. 44, 19 L. R. A. 371, 36 Am. St. Rep. 459; Phelps v. Manecke, 119 Mo. App. 139, 96 S. W. 221; Quirk v. Muller, 14 Mont. 467, 36 Pac. 1077, 25 L. R. A.

87, 43 Am. St. 647; Hughes v. Mulling, 36 Mont. 267, 92 Pac. 758; Lyon v. Husaey, 82 Hun, 15, 31 N. Y. S. 281; In re Schapiro, 144 N. Y. App. D. 1, 128 N. Y. S. 852; Manufacturers' Ac. Inspection Bureau v. Everwear Hosiery Co., 152 Wis. 73, 138 N. W. 624, 42 L. R. A. (N. S.) 847, Ann. Cas. 1914 C. 449. Cf. Lucas v. Pico, 55 Cal. 126; J. J. Case etc. Co. v. Fisher, 144 la. 45, 122 N. W. 575; Smith v. Hart-sell, 150 N. C. 71, 63 S. E. 172, 22 L. R. A. (N. S.) 203; Chandler v. Mason, 2 Vt. 193; Cobb v. Cowdery, 40 Vt 25, 94 Am. Dec. 370.

30 Hare v. McGue (Cal.), 174 Pac. 663, L. R. A., 1918 F. 1099; Wood v. Casserleigh, 30 Colo. 287, 71 Pac. 360, 97 Am. St. Rep. 138; J. I. Case Threshing Mach. Co. o. Fisher, 144 Iowa, 45, 122 N. W. 575; Singer Mfg. Co. v. City Nat. Bank, 145 N. C. 319, 59 S. E. 72; Manufacturers, etc., Bureau v. Everwear Hosiery Co., 152 Wis. 73, 138 N. W. 624, 42 L. R. A. (N. S.) 847, Ann. Cas. 1914 C. 449. Such a contract was upheld though the compensation was contingent on the success of the litigation in Haley v. Hollenback, 53 Mont. 494, 165 Pac. 459.

31 See supra, Sec. 33. The question of public policy was discussed in Furman v. Parke, 21 N. J. L. (1 Zab.) 310, and able to bargain for the suppression of evidence by paying witnesses to leave the State or otherwise than to bargain for its production; and any agreement having this for its object is invalid.32