Demand of illegal gratification is sine qua non for constituting an offence under the Prevention of Corruption Act, 1988. Mere recovery of tainted money is not sufficient to convict the accused, unless there is evidence to prove payment of bribe or to show that the money was taken voluntarily as a bribe. While invoking the provision of statutory presumption u/s 20 of the Act, the court is required to consider the explanation offered by the accused, if any, only on the touchstone of preponderance of probability and not on the touchstone of proof beyond all reasonable doubt. However, before the accused is called upon to explain how the amount in question was found in his possession, the foundational facts must be established by the prosecution. The complainant is an interested and partisan witness, concerned with the success of the trap, and his evidence must be tested in the same way as that of any other interested witness. In a proper case, the court may look for independent corroboration before convicting the accused.