What was truth serum? Well there was the chemical that muggles used in interrogation with suspects but Orr felt certain that magical truth serum did much more than that.

Orr put up her hand and waited for Professor Lafay to call on her before saying. "Well, Professor. I don't know about magical truth serums but I do know that muggles use a chemical compound that when administered to a person will cause them to unwittingly tell the truth about anything. So I'm assuming that magical truth serums do the same?"