Collins v. State, 175 P. 124 (Okla. 1918)

The subject of firearms and the size of bullets shot by different kinds of pistols is not a subject upon which the ordinary layman would be qualified to express an opinion; but this witness, having been a peace officer for many years, and having shown himself to be familiar with the use of firearms and the manner in which the same were loaded, and also With the different kinds of cartridges and bullets used in various kinds of firearms, was qualified, after a comparison of the same, to give, in our opinion, as an expert, his opinion as to whether or not the bullets introduced in evidence were of the same size. The bullets themselves were permitted to be introduced in evidence, and this character of demonstrative evidence is always permissible where material to the issues, and in this case we think it clearly established that the evidence was material.