What is the test for determining whether a defendant has a mental defect?

It is not the function of this court to judge expert psychiatric testimony quantitatively. The jury must evaluate the expert's credibility and weigh his testimony. Nagell v. United States, 392 F.2d 934, 937 (5th Cir. 1968).

After weighing the expert's credibility and the facts upon which he based his diagnosis, the jury may disregard his testimony if other evidence is more persuasive. United States v. Ingman, 426 F.2d 973, 976-977 (9th Cir. 1970).

There was a doubt here that Julian even had a mental disease or defect. There was evidence that his behavior could have resulted from either a neurotic character disorder or from a sociopathic personality. Testimony of his parents was consistent with either diagnosis. On these facts reasonable men would not necessarily have a reasonable doubt as to his sanity. Blake v. United States, 407 F.2d 908, 912-913 (5th Cir. 1969).

The diagnosis of appellant's psychiatric expert was based on subjective sources, the statements of Julian and his parents. The government's expert based his diagnosis on objective testing. The jury could reasonably have found that the defense expert based his opinion on erroneous facts. United States v. Ingman, supra.

Affirmed.