A trap is a procedure used to catch a public servant accepting a bribe. The complainant files a case stating a public servant demanded a bribe. An investigation is done and if the complaint is genuine, permission is given to lay a trap. For the trap, the complainant is given money coated in phenolphthalein powder to pay the bribe. Officers witness the exchange and arrest the public servant if a phenolphthalein test turns positive, indicating they handled the money. A successful trap provides strong evidence of guilt in corruption cases against public servants.