A woman walks into a drugstore, goes right up to the pharmacist, looks him straight into his eyes and says, "I would like to buy some cyanide,"
He looks at her and raises an eyebrow, "Why in the world do you need cyanide?"
She replies, "I need it to poison my husband."
The pharmacist's eyes get really big and he sputters, "Good lord lady, I can't give you cyanide to kill your husband. That's against the law. I'll lose my license and the authorities will throw us both in jail. It's murder! Absolutely not, I won't sell you any cyanide!"
The lady then pulls a photo out of her purse showing her husband in bed with the pharmacist's wife.
The pharmacist examines the picture for a long moment, then hands it back saying "Well, why didn't you tell me you had a prescription? How much do you need?"