ordinary man, unskilled and inexperienced, would not possess, and the ability to use them must have come from the study of treatises on such subjects, and from teaching and experience, to such an extent as to entitle the persons so testifying to be considered by the courts as qualified to express an accurate and sound opinion on the matters and things under investigation. Thus it appears how, in such cases, a departure became essential to the successful administration of justice, from the strict rule that witnesses shall testify solely to matters of fact and observation, and why it has long been considered that some witnesses must be allowed to testify to opinions and conclusions. Again, in a like case, a body is found bearing evidences of wounds or bruises. The question to be determined is whether they were inflicted before or after death; if before death, whether they were sufficient to cause death. Some wounds and injuries might be sufficiently apparent and dangerous so that the common, inexperienced eye would at once detect that they were sufficient to cause death. But in most instances this is not the case, and in such instances the testimony of experts is required by the necessity of the case, to show that the wounds and injuries were sufficient to cause death. _The General Rules Stated as to Subjects for Expert Testimony._—Hence the general rule is, that wherever the facts to be investigated are such that common experience and knowledge of men do not enable them to draw accurate conclusions, but are such that the study and experience of specialists do enable such specially endowed persons to draw accurate conclusions, then the inferences and deductions they have drawn can be testified to by those who qualify themselves before the court as persons having sufficient skill and experience as such specialists to entitle them to give opinions. The cases in which expert testimony is permitted to be given are set forth in Rogers on Expert Testimony, Sec. 6, quoting from Jones _v._ Tucker (41 N. H., 546), as follows: “1. Upon questions of science, skill, or trade, or others of like kind. “2. Where the subject-matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment without such assistance. “3. Where the subject-matter of investigation so far partakes of the nature of science as to require a course or previous habit of study in order to the attainment of knowledge of it.” So also Chief Justice Shaw of the Supreme Court of Massachusetts, in New England Glass Co. _v._ Lovell (7 Cushing, 319), said: