A woman walks into the drugstore and tells the pharmacist she wants to
buy some arsenic.

"What do you want with arsenic?" asks the pharmacist.
"I want to kill my husband because he's cheating on me by having sex
with another woman," the lady replies.
"I can't sell you arsenic so you can kill your husband, lady, even if
he is having sex with another woman," the pharmacist says.

The woman then reaches into her pocket and pulls out a picture of
her husband having sex with the pharmacist's wife and hands it to him.

"Oh, I didn't realize you had a prescription," the pharmacist replies.