Before becoming a probation officer, I worked loss prevention years ago, and caught hundreds of shoplifters. I have had to call many, many parents to tell them I had their child. Some parents would even argue with me on the phone - telling me that I must be mistaken because their kid couldn't have done such a thing.
I learned a long time ago that U can be the best parent in the world - but when that kid is with friends or leaves the house, they are still capable of anything. Scientific studies have also shown that due to changes in the brain in the teen years, teenagers doin't always think the same as a rational adult. So when U ask them "why did U do that," and they answer "I don't know," quite often they DO NOT know why they did a stupid thing or made a stupid decision.