OPINION. In Evidence. An infer ence or conclusion' drawn by a witness, as dis tinguished from facts known to him as facts.
2. It is ,the province of the jury to draw inferences and conclusions; and if witnesses were in general allowed to testify wbat they judge as well as what they know, the verdict would sometimes prove not the decision of the jury, but that of the witnesses. Hence the rule that, in general, the witness cannot be asked his opinion upon a particular ques tion. 29 N. H. 94 ; 16 Ill. 513 ; 18 Ga. 194, 573 ; 7 Wend. N. Y. 560 ; 24 id. 668 ; 2 N. Y. 514 ; 9 id. 371 ; 17 id. 340.
Some confusion in the application of this rule arises from tbe delicacy of the line which divides that which is to be regarded as matter of observation from that which is matter of judgment founded upon observa tion. Thus, it is held that an unprofessional witness may testify to the fact that a person whom he saw was intoxicated, wbether he is able to state all the constituent facts which amount to drunkenness or not. 14 N.Y. 562; 26 Ala. N. s. 26. But, on the other hand, in sanity or mental incapacity cannot, in geaeral, be proved by the mere assertion of an unpro fessional witness. 17 N. Y. 340 ; 7 Barb.N. Y. 314 ; 13 Tex. 568. And see 25 Ala. N. s. 21.
3. So handwriting may be proved by being recognized by a witness who has seen other writings of the party in the usual course of • business, or who has seen him write. Peake, Nisi P. 21 ; 1 Esp. 15, 351 ; 2 Johns. Cas. N. Y. 211 ; 19 Johns. N. Y. 134. But, on the other band, the authorship of an anonymous article in a newspaper cannot be proved by one professing to have a knowledge. of the author's style. How, App. Cas. N. Y. 187, 202.
From necessity, an exception to this rule of excluding opinions is made in questions in volving matters of science, art, or trade, where skill and knowledge possessed by a witness, peculiar to the subject, give a value to his opinion above that of any inference which the jury could draw from facts which he might state. 4 Iiill, N. Y. 129 ; 1 Den. N. Y. 281 ; 3 Ill. 297 ; 2 N. H. 480 ; 2 Stor. C.
C. 421. Such a witness is termed an expert ; lnd he may give his opinion in evidence.
4. The following reference to some of the matters in which the opinions of expert wit. nesses have been held admissible will Him, trate this principh. The unwritten or coni
mon law of foreign countries may be proved hy the opinion of witnesses possessing pro fessional knowledge, Story, Confl. of L. 530 ; 1 Cranch, 12, 38; 2 id. 236 ; 6 Pet. 763 ; Pet,. C. C. 225 ; 2 Wash, C. C. 1, 175 ; 2 Wend. N. Y. 411 ; 5 id. 375 ; 3 Pick. Masa. 293 ; 4 Conn. 517 ; 6 id. 486 ; 4 Bibb, Ky. 73 ; 2 Marsh. Ky. 609 ; 5 Harr. & J. Md. 186; 1 Johns. N. Y. 385 ; 3 id. 105 ; 14 Mass. 455 ; 6 Conn. 508 ; 1 Vt. 336 ; 15 Serg. & R. Penn. 87 ; 1 La. 153 ; 3 id. 53 ; 6 Cranch, 274 ; see, also, 14 Serg. & R. Penn. 137 ; 3 N. H. 349; 3 Yeates, Penn. 527 ; 1 Wheel. Crim. Cas. N. Y. 205 ; 6 Rand. Va. 704 ; 2 Russell, Crimes, 623 ; 4 Campb. 155 ; Russ. & R. 456; 2 Esp. 58 ; 3 Phil', 449 ; 1 .Eccl. 291 ; the degree of hazard of property insured against fire, 17 Barb. N. Y. 111 ; 4 Zabr. N. J. 843 ; handwriting, 35 Me. 78 ; 2 R. I. 319; 25 N. H. 87 ; 1 Jones, No. C. 94, 150; 13 B. Monr. Ky. 258 ; mechanical operations, the proper way of conducting a particular manu facture, and the effect of a certain method, 4 Barb. N. Y. 614 ; 19 id. 338 ; 3 N. Y. 322; negligence of a navigator, and its effect in producing a collision, 24 Ala. N..s. 2I sanity, Add. 244 ; 12 N. Y. 358 ; 17 id. 340 ; impotency, 3 Phill. Eccl. 14 ; value of chattels, 22 Ala. x. s. 370 ; 11 Cush. Mass. 257 ; 22 Barb. N. Y. 652, 656 ; 23 Wend. N. Y. 354 ; value of land, 11 Cush. Mass. 201 ; 4 Gray, Mass. 607 ; 9 N. Y. 183 ; com pare 4 Ohio St. 583 ; value of 'services, 15 Barb. N. Y. 550 ; 20 id. 387 ; benefit to real property by laying out a street adjacent thereto, 2 Gray, Mass. 107 ; survey-marks identified as being those made by United States surveyors, 24 Ala. x. s. 390 ; sea worthiness, Peake, Cas. 25 ; 10 Bingh. 57 And see 9 Cush. Mass. 226. So an engineer may be called to say what, in his opinion, is the cause that a harbor has been blocked up. 3 Dougl. 158; 1 Phi llipps, Ev. 276 ; 4 Term, 498.
5. It is to be observed, however, that the principle of admitting such opinions is taken with the qualifications necessary to make, as far as possible, the judgment of the jury, and not that of the witness, the final means of determining the issue. Thus, opinions of ex perts are not admissible upon the question of damages, 4 Den. 311 ; 3 Hill, N. Y. 609 ; 21 Barb. g. Y. 331 ; 23 Wend. N. Y. 425 ;