Case Name: Lessee of John Forbes against Armstrong Caruthers and Andrew Caruthers
Court: Supreme Court of Pennsylvania
Jurisdiction: Pennsylvania
Decision Date: 1803-05
Citations: 3 Yeates 527
Docket Number: 
Parties: Lessee of John Forbes against Armstrong Caruthers and Andrew Caruthers.
Judges: CORAM, YEATES AND SMITH, JUSTICES.
Reporter: Reports of cases adjudged in the Supreme Court of Pennsylvania (Yeates)
Volume: 3
Pages: 526–527

Head Matter:
*AT A CIRCUIT COURT, HELD AT CARLISLE,
MAY, 1803.
CORAM, YEATES AND SMITH, JUSTICES.
Lessee of John Forbes against Armstrong Caruthers and Andrew Caruthers.
Mere opinion is no evidence; but the opinion of men of science on facts stated, may be received, to inform the jury.
Ejectment for lands in Pennsbro’ township.
The plaintiff claimed under a survey made in 1744, which called for John Ruddock’s lands on the three last courses, and was bounded by Coneodogwinet creek. The survey would not close on protraction, and in order to reach Ruddock’s line, it required that the second line should be extended 40 perches, and to come to the creek that the third line should be extended 40 perches.
It was evident therefore that some error had obtained in the survey, and it was asserted on the part of the defendants, that it must have arisen from the first line being called 278 perches in length instead of 225 perches. This line had been run the day preceding the plaintiff’s survey for William Dunbar, by the some surveyor.
Cited in 67 Pa. 421 in support of the decision that the opinion of a witness acquainted with the facts, of the total or aggregate loss or value of injury, is evidence as to the amount, without describing the elements in detail.
Cited in 95 Pa. 138; io W. N. C. 328, in support of the proposition that a practical surveyor may testify whether in his opinion certain marks on trees, piles of stones or other marks on the ground were intended as monuments of boundaries.
Cited in 108 Pa. 449; 16 W. Ñ. C. 466, to show that in Pennsylvania it has always been the rule that after a non-professional witness has stated the facts upon which his opinion is founded he is permitted to state his opinion as to the sanity or insanity of the testator.
Samuel Lyon, esq. was offered as a witness to shew how in his opinion the mistake must have originated, and was opposed by the plaintiff’s counsel.
Messrs. Hamilton and Watts, pro quer.
Messrs. Duncan and C. Smith, pro def.

Opinion:
Sed per cur.
Mere abstract opinion is not evidence; but a surveyor, or any other person conversant in the subject, may state facts, and his opinion on those facts, to enable the jury to form a correct judgment of the matter in dispute. It is general information in a question of science, which others unacquainted with the subject must necessarily want. Thus a physician, who has not seen the particular patient, may, after hearing the evidence of others, be called to prove on his oath, the general effects of a particular disease, and its probable consequences in the particular case. Peake on Evid. 137.