He therefore contends that the trial judge erred in failing to recuse himself sua sponte. • 12 While it cannot be disputed that in a criminal trial a judge's hostile attitude toward the defendant, or his witnesses, is apt to prejudicially influence the jury in arriving at its verdict (see People v. Marino (1953), 414 Ill. 445, 111 N.E.2d 534), and that it may be better for a judge to recuse himself when he learns that a plea of guilty has been offered ( United States v. Walker (D.C. Cir. 1972), 473 F.2d 136, 138), a trial judge is under no duty to recuse himself even from a bench trial because he presided at the trial of co-defendants (see People v. Smith (1965), 32 Ill.2d 88, 93-94, 203 N.E.2d 879; People v. Smith (1975), 29 Ill. App.3d 519, 331 N.E.2d 99, cert. denied (1976), 424 U.S. 925, 47 L.Ed.2d 334, 96 S.Ct. 1137 (abstract)), or even because he presided at a prior trial of the same defendant in the same cause (see United States v. Dichiarinte (7th Cir. 1971), 445 F.2d 126, 132). • 13 Moreover, the alleged bias or prejudice of a trial judge to be disqualifying must be shown to have stemmed from an extra-judicial source and result in an opinion on the merits on some basis other than what the judge learned from his participation in the case.

The basis for this rule is the recognition that a trial judge possesses the ability to determine the factual issues based only upon legally relevant and competent evidence introduced at trial, and will not let any personal bias, prejudice or irrelevant material enter into his determination. ( People v. Smith (1975), 29 Ill. App.3d 519, 331 N.E.2d 99.) Likewise, there can be no assumption of any inherent prejudicial effect on the trial judge merely from his having heard the excluded hearsay references. ( People v. Smith.) As the Federal Third Circuit Court of Appeals said in United States ex rel. Bennett v. Myers (3rd Cir. 1967), 381 F.2d 814, 818: "There would be a complete breakdown in the operation of the machinery of justice if we refused to recognize the capacity of a trial judge to put aside what he has heard if it is not legally relevant to the case." We conclude there is no merit to these contentions of Glanton and of Johnson.