This gal walks into the drugstore and tells the pharmacist she wants to buy some arsenic.

He says, "What do you want with arsenic?"

She said "I want to kill my husband. He cheats on me."

The pharmacist says, "Lady, I can't sell you arsenic to kill your husband, even if he is cheating on you!"

So, she reaches into her pocket and pulls out a picture of her husband having sex with the pharmacist's wife.

The pharmacist says, "I didn't realize you had a prescription."