BOM: Mosiah 3:16 At what age do children begin sinning?

At age 8 they are considered to be at the age of accountability. Don't ask me why that age, but that's the age that is set. At that age, they should be able to distinguish between right and wrong. They don't understand it all, and they certainly don't understand the whole concept of sin or the atonement. They can understand when they have done something wrong.