By his first assignment of error, defendant contends the court erred in granting the State’s motion to consolidate the *564cases against defendant and the case against Dean for trial. We find no merit in the assignment.
It is well settled in this jurisdiction that the question of consolidation of indictments against defendants charged with committing similar offenses at the same time and place is addressed to the sound discretion of the trial court. State v. Wright, 270 N.C. 158, 153 S.E. 2d 883 (1967) ; State v. Johnson, 280 N.C. 700, 187 S.E. 2d 98 (1972) ; State v. Arney, 23 N.C. App. 349, 208 S.E. 2d 899 (1974) ; State v. Locklear, 26 N.C. App. 26, 214 S.E. 2d 797 (1975). While recognizing this rule, defendant argues that his case should be an exception as was true in State v. Bonner, 222 N.C. 344, 23 S.E. 2d 45 (1942).
We find it easy to distinguish the cases. In Bonner, four defendants were charged individually and in separate bills of indictment with murder; at trial, the State relied heavily on confessions of two defendants separately made and on confessions of the other defendants jointly made; some of the confessions implicated other defendants who were not present when the confessions were made; and none of the defendants testified at the trial. Although the trial court instructed the jury to consider the confessions only as against the defendants making them, the Supreme Court held that the appealing defendants were prejudiced and should have been tried separately. In the case at hand, no confession is involved.
 By his second assignment of error, defendant contends the court erred in admitting into evidence a photograph allegedly portraying Carter’s head injuries after the robbery. The photograph, about which defendant complains, does not appear as a part of the record on appeal, therefore, no error is shown. There is a presumption in favor of regularity and it is incumbent on an appellant to show otherwise. 3 Strong, N. C. Index 2d, Criminal Law § 158, p. 108; State v. Hill, 9 N.C. App. 279, 176 S.E. 2d 41 (1970), rev’d on other grounds, 277 N.C. 547, 178 S.E. 2d 462 (1971).
 By his third assignment of error, defendant contends the court erred in allowing Sergeant Boyd, who qualifed as a fingerprint expert, to give opinion testimony as to the length of time the print in question had been on the cigar box. This assignment has no merit.
In matters requiring expert skill or knowledge, about which a person of ordinary experience would not be capable of form*565ing a satisfactory conclusion, the admission of expert opinion is necessary, and in such cases competent. Lindstrom v. Chesnutt, 15 N.C. App. 15, 189 S.E. 2d 749 (1972), cert. denied, 281 N.C. 757, 191 S.E. 2d 361 (1972). In the case at hand, the witness gave sound reason for his opinion, namely, the presence of moisture on the print and the fact that moisture on a fingerprint gradually disappears as the print gets older. The assignment of error is overruled.
We have carefully, considered the other assignments of error brought forward and argued in defendant’s, brief and find them also to be without merit.
Judges Parker and Clark concur.