You can have your juvenile record sealed, but an entity such as you mention would have access to it as well as whether you were ambidextrous.
The CIA will know about the conviction, but if you were 15 then it probably won't be a problem.
Seth Weinstein, Esq.
Practicing throughout Southern California
This reply should NOT be considered a legal opinion of your case / inquiry. At this time I do not have sufficient factual/legal documentation to give a complete answer to your question and there may be more to the issues you raised then I have set out in my brief reply.
If the juvenile court records haven't been sealed, hire an attorney and do so immediately. Have a local attorney run your criminal record and go to the juvenile court clerk's office and see what, if anything, is of record. An agency like the ATF&E, FBI, DEA, CIA, SS, etc., should be able to locate any prior record, expunged, sealed, or not.
I am trying to give you a general answer to your question. We do not have an attorney-client relationship by this response on the avvo website. I have not been retained to represent you. I am licensed to practice law in Kentucky and in federal court in this state and the Southern District of Indiana. You need to seek legal advice from an attorney licensed to practice in your area..
As my colleagues have advised, the CIA (and any other law enforcement or Department of Defense agency) will have your delinquency history. They'll probably also know all your love affairs, so be nice. :)
If you get far enough in to the application process, the CIA (or Treasury or FBI or DEA, etc) will give you what is known as a "lifestyle polygraph." This takes 6 to 8 hours. What they are primarily concerned with is whether you are deceptive with them. They also want to know if you have anything in your background which could subject you to blackmail, which could leave you vulnerable to enemy parties.
If you weren't charged (maybe I'm misreading your post) there will be no crime to be sealed. However, I can guarantee you that they will ask if you've ever committed a crime. They are not asking whether you were convicted; they want to know if you did something. You will have to tell them that you did. One of the few good things about a lifestyle poly is that they will probe you about the circumstances, and you can explain that this was when you were 15, etc etc etc.