After a trial by jury the defendant was convicted of robbery armed, MCLA § 750.529 (Stat Ann 1970 Cum Supp § 28.797). He now appeals, contending that the trial court erred in refusing to instruct the jury on the defense of insanity.

A person is presumed to be sane. Once the defendant has introduced evidence of insanity however, the prosecution has the burden of proving that he is sane. People v. Krugman (1966), 377 Mich 559; People v. Garbutt (1968), 17 Mich 9. The question here is whether defendant’s testimony can be regarded as evidence of insanity.

Although the defendant was provided with a psychiatrist, he chose not to call him as a witness, and, consequently, there was no evidence on which a jury could determine the issue of insanity.

It was defendant’s testimony that he had received treatment, primarily for alcoholism, in several mental institutions, that from time to time he suffered from blackouts, and that he had no recollection of his whereabouts when this crime was committed.

Determination regarding the issue of insanity requires inquiry into an accused’s state of mind at the time a criminal act is committed. Pacts such as prior institutional confinements or lack of recall regarding specific incidents are of little assistance in determining an individual’s state of mind at one point in time. There was no evidence introduced *256 on which a finding of insanity could he made; such a determination cannot be based on mere conjecture or speculation. Kregger v. Bannan (ED Mich, 1959), 170 F Supp 845. It was not error, therefore, for the trial court to refuse an instruction on the defense of insanity.

Affirmed.