Here is the thing about teens and their friends. They will go to extreme measures to protect them, even if it means lying. That emotional center of the brain, that is hard-wired in Adolescence to always be in the "on"position is full to the brim with love for friends. And when a friend needs you, there is no stopping them. Loyalty often gets in the way of good sense.
When does the job of being loyal to the people close to you no longer apply? Teens often find themselves in situations when this very dilemma is questioned, like with Dzhokhor and his roommates. There is nothing, and I mean nothing that stands in the way of a teen and their friends. If you so much as criticize even the most obvious fault in one of their buddies, the gauntlet is thrown down. The cardinal rule of "don't talk bad about my boy/girl has been broken, and you will pay dearly for breaking it.
This lack of objectivity about their friends can often put them in situations that are scary, and unsafe. They become caught in the bind of doing what they know is right, vs protecting their relationship at all costs. Perhaps your teen has a close friend that is depressed, perhaps even suicidal, is engaging in self-destructive behavior, has a serious eating disorder or is abusing drugs and/or alcohol. Maybe they have been with a friend who has been drinking or doing drugs, and though they won't get in the car with them, they won't grab the keys away from this compromised driver, leaving the fate of a possible drunk driving accident in the hands of their drunk friend. Loyalty, secrecy, and trust, these are powerful promises. The risk of losing this friend should they break this oath of loyalty is usually stronger than the reality of possibly literally losing their friend.
This case can be a used as a valuable tool to help your teen talk about their own issues of loyalty vs safety. Here is your " I Get it" moment. " Hey honey have you heard about this story with the Marathon Bomber and his college roommates. Pretty scary stuff isn't it. I get that these roommates felt protective of their friend and didn't want him to get in any trouble, and probably didn't even know what they were protecting him from since he had not yet been identified as the bomber. This is really hard stuff for a young person. I'm guessing there must be times that you are in a position of questioning whether you should do something you know is right but worry that it might get your friend in trouble. Maybe you have a friend who you worry is depressed, or you know drinks or does too many drugs, or is in a scary relationship and they talk to you about it but make you promise not to tell anybody. That is a lot of responsibility to carry around. I am always here to help you with this stuff and I promise I won't call their parents or the school, but I am here to help you deal with it all. I would never want you to think that loyalty trumps safety. Making sure that your friend is safe, is way more important than whatever secret they have given you to hold."
This is such an important issue to address with your teen. There is too much at stake not to.