A fact situation similar to the one described in Commonwealth v Cressinger (1899) 193 Pa 326, 44 A 433, supra, existed in Commonwealth v Spardute (1923) 278 Pa 37, 122 A 161, in which after the district attorney and other officials casually stated to the person accused of murder that they had certain evidence in their possession, among other things, that they had the knife with which the killing w