"14. If an offence takes place inside the privacy of a house and in such circumstances where the assailants have all the opportunity to plan and commit the offence at the time and in circumstances of their choice, it will be extremely difficult for the prosecution to lead evidence to establish the guilt of the accused if the strict principle of circumstantial evidence, as noticed above, is insisted upon by the courts. A judge does not preside over a criminal trial merely to see that no innocent man is punished. A judge also presides to see that a guilty man does not escape. Both are public duties. (See Stirland v. Director of Public Prosecutions (1944 AC 315) - quoted with approval by Arijit Pasayat, J in State of Punjab v. Karnail Singh (2003) 11 SCC 271). The law does not enjoin a duty on the prosecution to lead evidence of such character which is almost impossible to be led or at any rate extremely difficult to be held. The duty on the prosecution is to lead such evidence which it is capable of leading, having regard to the facts and circumstances of the case. Here it is necessary to keep in mind Section 106 of the Evidence Act which says that when any fact is especially within the knowledge of any person, the burden of proving that fact is upon him. Illustration (b) appended to this section throws some light on the content and scope of this provision and it reads: