Where deliberating jurors receive external information that a criminal defendant had committed prior bad acts, does the dissemination of such information to jurors necessarily violate his Sixth Amendment right to trial by an unbiased jury, or may the receipt of such information be excused as 'harmless error'?

question presented is: Where deliberating jurors receive external information that a criminal defendant had committed prior bad acts, does the dissemination of such information to jurors necessarily violate his Sixth Amendment right to trial by an unbiased jury, or may the receipt of such information be excused as “harmless error”? A secondary question presented is: Where courts violate Federal Rule of Evidence 606(b)’s provision barring evidence relating to the effect of external influences on the mental processes of jury members, can such evidence still be considered by the court in making its determination as to whether the defendant was prejudiced? i