A woman approaches the pharmacy counter and says "I'd like to buy some cyanide, please."
"Cyanide!" The pharmacist says, "why do you need cyanide, ma'am?"
"I'm going to poison my husband." she said matter-of-factly.
"I'm sorry ma'am, but I can't do that." The pharmacist explained, "poisoning your husband is illegal. I'd lose my license, and you would go to jail. I cannot give you cyanide."
He continued, "But may I ask, why is it that you want to kill your husband?"
She calmly showed the pharmacist to photograph of her husband in bed with the pharmacist's wife.
"Oh, I see. You didn't tell me you had a prescription."